VOXI or giffgaff: which cheap SIM is better? It depends on the network you need, not the logo. VOXI runs on Vodafone (and says it also uses the combined Vodafone and Three network). giffgaff runs on O2. Opensignal’s January 2026 UK report, using data from 1 October to 29 December 2025, put Vodafone’s overall download speed experience at 37.5 Mbps and O2’s at 32.8 Mbps, while O2 led overall coverage. On price, giffgaff’s 40GB plan at £8 a month for 18 months, for sign-ups before 4 December 2026, is the sharper data rate if 40GB is enough. VOXI’s 30-day plans start at £10 a month for 20GB plus data-free social apps (checked 10 November 2026), and can be cancelled any month. Which?’s January 2026 survey scored both at 79%, joint third of 15 providers.
Last updated: 10 November 2026. giffgaff prices from giffgaff.com, checked 10 November 2026. VOXI plan prices from voxi.co.uk, checked 10 November 2026. Opensignal data covers 1 October to 29 December 2025. Check the plan page before you pay, because allowances can change.
We may earn a commission if you buy through the deal buttons on this page. It does not change the price you pay. The three buttons go to giffgaff plans; confirm any VOXI price on voxi.co.uk or in our VOXI review before you switch.
giffgaff 40GB — £8/mo · 18-month plan
- 40GB of 5G data, unlimited UK calls and texts, £8 a month on giffgaff.com, checked 10 November 2026, for sign-ups before 4 December 2026
- 18-month plan on O2’s network (giffgaff), with no credit check
- Main limitation: giffgaff lists the 40GB for £8 plan as 6GB plus 34GB extra for 18 months. Confirm the £8 price and terms before you pay
VOXI vs giffgaff at a glance
VOXI | giffgaff | |
|---|---|---|
Host network | Vodafone (VOXI also describes this as the combined Vodafone and Three network) | O2 |
Contract | 30-day rolling, price-locked while you stay on the plan | 18-month plans and rolling or pay-as-you-go goodybags |
Entry plan (checked 10 November 2026) | £10 a month for 20GB, plus data-free social apps, 30 days | 40GB for £8 a month for 18 months, for sign-ups before 4 December 2026 |
Bigger data | £12 for 75GB and £20 for 300GB during VOXI’s 3x offer, which VOXI lists until 26 November 2026 (then 25GB and 100GB) | 100GB for £15 a month on 18 months, £270 over 18 months; giffgaff also listed a Black Friday 200GB plan at £12 a month on an 18-month plan (activate by 7 December 2026), both checked 10 November 2026 on giffgaff.com |
Unlimited | £35 a month, checked 10 November 2026 | £25 a month on an 18-month plan, checked 10 November 2026 |
Which? customer score (January 2026) | 79%, joint third of 15 | 79%, joint third of 15 |
EU roaming | Included only in Ireland, the Isle of Man, Iceland and Norway; a pass is needed elsewhere, from £2.60 a day on 20 October 2026 | Up to 5GB of EU roaming data in 37 destinations on every plan (giffgaff.com, checked 10 November 2026) |
Our VOXI review and giffgaff review set out the full plan tables. For a Three-network alternative to both, see giffgaff vs Smarty guide. You can also browse SIM only deals and VOXI SIM only deals.
Is VOXI faster than giffgaff?
Not in a way you can take for granted at your own address. Speed follows the host network. Opensignal’s January 2026 UK Mobile Network Experience report gave Vodafone an overall download speed experience of 37.5 Mbps and O2 32.8 Mbps. On 5G downloads, Vodafone averaged 130.9 Mbps and O2 89.9 Mbps. EE led overall download speed, at 53.2 Mbps, and Three led 5G download speed, at 187 Mbps. O2 retained the coverage experience award. Those figures are national averages from 1 October to 29 December 2025, not a promise about your kitchen or your commute.
VOXI’s own site describes the brand as running on the combined Vodafone and Three network. Which? has described VOXI as a virtual provider using Vodafone’s infrastructure. In practice, you should still check your postcodes on Vodafone’s network checker and on Ofcom’s mobile and broadband checker. If O2 is the only network that works indoors where you live, giffgaff will be the more reliable of these two, even if Vodafone looks faster on a national chart.
Is VOXI actually good?
For a no-contract SIM on Vodafone’s network, yes, with clear catches. Which? VOXI review and ISPreview’s write-up of the Which? 2026 mobile results report a Which? customer score of 79% in the January 2026 survey of 5,137 customers, joint third of 15 providers, level with giffgaff and Smarty. Only Talkmobile (83%) and Tesco Mobile (81%) scored higher. Trustpilot reviews of VOXI showed a TrustScore of 3.3 out of 5 from 23,931 reviews on 20 October 2026, with praise for flexible plans and complaints about website problems, number-transfer delays and a chatbot that is hard to escape. Trustpilot also noted that VOXI had not recently invited reviews, so that mix may not be representative.
The product itself is simple: 30-day plans, no annual price rise, and data-free social apps on the cheaper plans, which is the main reason people pick VOXI over a plain data bundle. The weak spots are roaming in most of Europe, a dear unlimited plan at £35 a month (checked 10 November 2026), and temporary data boosts. VOXI lists the 3x data offer on the £12 and £20 plans until 26 November 2026, after which those plans return to 25GB and 100GB. Judge the plan on what it will give you after that date, not only on the boosted figure.
Why is VOXI so cheap?
VOXI is a virtual brand. It does not run its own radio network. It sells online, on a 30-day rolling basis, with no shops and no credit check of the sort you get on a 24-month phone contract. That keeps the overhead down. The £10 plan also puts several social apps outside your data allowance in the UK, so heavy Instagram or TikTok use can look cheaper than the 20GB headline suggests. It is not cheap in every direction. Unlimited data was £35 a month (checked 10 November 2026), and roaming outside a short list of countries needs a paid pass. Cheap here means no contract and a low entry price, not the lowest price for every type of use.
What are the top 5 best mobile networks in the UK?
There is no official top five, and these two brands are virtual operators, not the radio networks themselves. The four host networks are EE, O2, Vodafone and Three. In Opensignal’s January 2026 UK Mobile Network Experience report, EE had the best overall download speed experience at 53.2 Mbps, Three was second at 51 Mbps, Vodafone third at 37.5 Mbps and O2 fourth at 32.8 Mbps. O2 led overall coverage, and EE led 5G coverage experience. Which?’s January 2026 customer scores put Talkmobile, Tesco Mobile, then VOXI, giffgaff and Smarty in a tight group at the top of that survey, which is about service and value, not speed tests. If you want a “best network” answer for your own street, run the coverage checkers rather than picking a national winner.
Plans and prices compared
Plan | Data | Monthly price | Contract | Network |
|---|---|---|---|---|
giffgaff 40GB | 40GB (6GB plus 34GB extra for 18 months) | £8 | 18 months, sign-ups before 4 December 2026 | O2 (giffgaff) |
giffgaff 100GB | 100GB | £15 | 18 months | O2 (giffgaff) |
giffgaff 15GB pay as you go | 15GB | £10 | One-month top-up | O2 (giffgaff) |
VOXI £10 | 20GB, plus data-free social apps | £10 | 30 days, rolling | Vodafone (VOXI) |
VOXI £12 | 75GB during the 3x offer, then 25GB after 26 November 2026 | £12 | 30 days, rolling | Vodafone (VOXI) |
VOXI £15 | 35GB, plus data-free apps | £15 | 30 days, rolling | Vodafone (VOXI) |
VOXI £20 | 300GB during the 3x offer, then 100GB after 26 November 2026 | £20 | 30 days, rolling | Vodafone (VOXI) |
VOXI unlimited | Unlimited | £35 | 30 days, rolling | Vodafone (VOXI) |
giffgaff prices in the table were checked on giffgaff.com on 10 November 2026. VOXI prices were checked on voxi.co.uk on 10 November 2026. The 40GB giffgaff plan is 6GB with 34GB extra for the 18-month term when you sign up before 4 December 2026, so read what happens if you stay after that term. VOXI’s £15 plan gives 35GB plus data-free social, music and video on 20 apps. That is the same app list as the £12 plan, so it only makes sense if you want an allowance that stays the same after 26 November.
giffgaff 100GB — £15/mo · 18-month plan
- 100GB of 5G data with unlimited UK calls and texts, £15 a month on an 18-month plan (£270 over 18 months), checked 10 November 2026 on giffgaff.com
- giffgaff also listed a Black Friday 200GB plan at £12 a month on an 18-month plan (activate by 7 December 2026), checked 10 November 2026, which is more data for less than this 100GB plan. Check giffgaff.com for that offer before you choose; the button below is the 100GB plan
- Main limitation: this 100GB plan is undercut by that 200GB Black Friday price, so only use this button if the 200GB plan is not right for you
Who should pick VOXI, and who should pick giffgaff?
If you… | Better pick | Why |
|---|---|---|
Need a signal on O2 at home | giffgaff | It uses O2’s masts. VOXI will not fix a weak Vodafone signal |
Need a signal on Vodafone | VOXI | Same radio network, without a Vodafone-brand contract |
Want 40GB at a low monthly price and can commit | giffgaff 40GB at £8 | £144 over 18 months, checked 10 November 2026 on giffgaff.com |
Live on social apps and want a 30-day plan | VOXI’s £10 plan | 20GB plus data-free social apps, cancellable any month |
Want lots of data with no long contract | Compare VOXI’s £20 plan after 26 November (100GB) with other rolling SIMs | The 300GB boost is temporary |
Want unlimited data | Probably neither of these two at full price | VOXI’s unlimited plan was £35 a month (checked 10 November 2026) |
Roam often in Europe | Check both sets of terms, and lean away from VOXI if you leave Ireland, Iceland or Norway | VOXI’s pass starts at £2.60 a day on 20 October 2026 |
How to switch between VOXI and giffgaff
Check coverage at the postcodes you actually use, not just a national average.
If you are still in a minimum term with another network, ask about an exit fee. Rolling plans do not have one.
To keep your number, ask your current provider for a PAC code (text PAC to 65075). A STAC code cancels your old contract without moving the number. Codes are usually issued quickly.
Order the new SIM or eSIM and enter the code when the new provider asks for it.
Keep the old SIM until the number has moved and you have a signal on the new one.
eSIM availability depends on your handset and on the brand, so check during the order. 5G needs a 5G phone and coverage in that spot.
giffgaff 15GB pay as you go — £10 for one month
- 15GB for £10 for one month with no contract, checked 10 November 2026 on giffgaff.com
- Useful if you want O2 coverage without an 18-month plan
- Main limitation: it is a one-month top-up, so the price can change when you next buy data
FAQ
Is VOXI faster than giffgaff?
It can be, but only where Vodafone is stronger than O2. Opensignal’s January 2026 report put Vodafone’s overall download speed experience at 37.5 Mbps and O2’s at 32.8 Mbps, with Vodafone also ahead on 5G downloads. O2 led overall coverage. Check your own postcodes before you treat those averages as a reason to switch.
Is VOXI actually good?
Yes, for many people who want a 30-day Vodafone SIM with data-free social apps. Which? scored it 79% in January 2026, joint third of 15 providers, the same score as giffgaff. The catches are paid roaming in most of Europe, a £35 unlimited plan (checked 10 November 2026), and data boosts that VOXI lists until 26 November 2026.
Why is VOXI so cheap?
It is an online-only virtual brand on Vodafone’s network, with 30-day plans and no high-street shops. The £10 plan also leaves some social apps outside your data allowance in the UK. Unlimited data and European roaming are not the cheap parts of the range.
What are the top 5 best mobile networks in the UK?
There is no official top five. Opensignal’s January 2026 report ranked EE, Three, Vodafone and O2 in that order for overall download speed, with O2 first for overall coverage. Which?’s January 2026 customer survey put Talkmobile and Tesco Mobile first and second, with VOXI, giffgaff and Smarty joint third on 79%. Your street can disagree with any national table.
Which is cheaper, VOXI or giffgaff?
If 40GB is enough and you can take an 18-month plan, giffgaff’s £8 plan, checked 10 November 2026 on giffgaff.com, is cheaper than VOXI’s £10 entry plan. If you want a 30-day plan and data-free social apps, VOXI can work out better than a plain 20GB bundle. Unlimited data was much cheaper on other networks than on VOXI’s £35 plan (checked 10 November 2026).
Can I keep my number if I switch?
Yes. To keep your number, ask your current provider for a PAC code (text PAC to 65075) and give it to the new one. A STAC code cancels your old contract without moving the number. The number usually moves in one working day once the new SIM is active, though some customers report delays. Keep the old SIM until you have a signal on the new plan.
Does giffgaff have a credit check?
giffgaff says its SIM plans do not need a credit check. That is one reason it suits people who want to avoid a 24-month phone contract. You still need to pay each month on time, and an 18-month plan is a commitment even without a credit search.
Sources: Opensignal’s January 2026 UK Mobile Network Experience report (data collected 1 October to 29 December 2025); Which? VOXI review; ISPreview’s write-up of the Which? 2026 mobile results; Trustpilot reviews of VOXI (20 October 2026); plan prices from voxi.co.uk and giffgaff.com (checked 10 November 2026); our VOXI review and giffgaff review.
