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Unlimited Data SIM-Only Deals

Compare 10 unlimited data SIM-only plans from GiffGaff, Smarty, Lebara and 1pMobile from £15.00/mo. Refreshed daily for May 2026.

10 plans matching Unlimited

Network Plan Data Mins / Texts Term 5G EU Roam Monthly
GiffGaff 300GB Unlimited Unlimited mins / Unlimited texts 18 months 5G Yes £15.00 /mo Get plan
Smarty Unlimited Unlimited Unlimited mins / Unlimited texts 1 month rolling 5G Yes £18.00 /mo Get plan
GiffGaff golden goodybag Unlimited Unlimited mins / Unlimited texts 1 month rolling 5G Yes £20.00 /mo Get plan
Lebara 12 Month Plan Unlimited 1 Unlimited Unlimited mins / Unlimited texts 12 months 5G - £22.50 /mo Get plan
GiffGaff Unlimited Unlimited Unlimited mins / Unlimited texts 18 months 5G Yes £25.00 /mo Get plan
1pMobile Unlimited Unlimited Unlimited mins / Unlimited texts 1 month rolling 5G Yes £25.00 /mo Get plan
Lebara Unlimited Unlimited Unlimited mins / Unlimited texts 1 month rolling 5G - £25.00 /mo Get plan
Lebara 12 Month Plan Unlimited 2 Unlimited Unlimited mins / Unlimited texts 12 months 5G - £27.00 /mo Get plan
Lebara Unlimited Unlimited Unlimited mins / Unlimited texts 1 month rolling 5G - £30.00 /mo Get plan
GiffGaff golden goodybag Unlimited Unlimited mins / Unlimited texts 1 month rolling 5G Yes £35.00 /mo Get plan

Unlimited data SIM-only plans explained

Unlimited data plans remove the monthly data cap entirely - useful if you stream video on the move, hotspot to a laptop, or use your phone as your primary internet connection. On most UK networks, unlimited genuinely means unlimited for normal phone use, with a soft fair-use cap (often around 600GB per month) only kicking in for heavy tethering. The cheapest path to unlimited is almost always a 12-month contract, where the longer commitment unlocks a meaningful discount over the rolling rate, and pairing unlimited with 5G coverage is what makes mobile broadband and tethering genuinely usable. Some plans tier the unlimited tag across speed bands - Vodafone Lite, Unlimited and Unlimited Max, for instance, all unlimited but capped at different peak download speeds. Three and EE keep things simpler with a single unlimited tier. MVNOs running on the host networks (Smarty on Three, iD Mobile on Three, giffgaff on O2) typically undercut the host by a meaningful margin for the same allowance, so check both before committing. Unlimited is overkill if you mainly use Wi-Fi at home and work - a 30-50GB plan will save you several pounds a month and easily cover normal mobile use.

Frequently asked questions

What is a SIM-only plan?
A SIM-only plan is just airtime - calls, texts and mobile data on a SIM card you slot into a phone you already own. There is no handset bundled in, so you pay only for the network service. Plans range from rolling 30-day deals you can cancel any time, up to 24-month contracts with bigger data allowances at lower monthly prices.
What is the difference between SIM-only and a phone contract?
A phone contract bundles a handset and an airtime plan into one monthly payment, usually over 24 or 36 months. A SIM-only plan is airtime only, so it is cheaper month-to-month and you keep using whatever phone you already own. If your current phone still works, a SIM-only plan almost always saves money compared with upgrading to a new contract.
Can I keep my phone number when I switch SIM-only plans?
Yes. Text PAC to 65075 from your existing SIM and your current network will reply with a PAC code that lets you transfer your number to the new SIM. The switch usually completes within one working day and is free under Ofgem rules.
Read the full PAC code guide
How long does SIM activation take?
Most SIMs activate within a few hours of you putting them in your phone, though the network can take up to 24 hours to switch your number across if you used a PAC code. Until activation completes you may briefly lose service on the old SIM.
Can I cancel a SIM-only plan?
Rolling 30-day SIM-only plans can be cancelled with 30 days notice with no penalty. Fixed 12-month or 24-month SIM-only contracts have an early termination fee, usually the remaining monthly charges discounted by a few percent. Always check the terms before committing to a longer plan.
Is unlimited SIM-only data really unlimited?
On most major networks, yes - there is no hard cap. A few plans have a fair-use throttle if you tether more than ~600GB in a month, but for normal phone use it is genuinely unlimited.
What network is best for unlimited data?
EE and Three traditionally offer the broadest 5G + unlimited combos. Vodafone Unlimited Max and O2 Unlimited are competitive too. MVNOs like Smarty (on Three) and iD Mobile (on Three) usually undercut the host network on price.