Mobile
Best SIM Only Deals? What to Check Before You Switch
The right SIM-only plan depends on what you use. Check the data you actually get through each month, whether you want a rolling plan or a fixed term, and the price over the whole term including any stated rise.
- Data you actually use
- Rolling or fixed term
- The whole-term price
Plans from the providers Wisemium works with. Wisemium does not sell mobile plans itself. Keeps the price, the data and the end date on record.
Your SIM-only plan
- Data used
- From your bill
- Term
- Rolling or fixed
- Contract end date
- On record
Example. Your own details appear once you add them.
Rolling or fixed term
30-day rolling
- Tied in
- For a month at a time
- Suits
- Flexibility, or a short stay
12 or 24 months
- Tied in
- For the term, with an exit fee
- Suits
- A known need, often at a lower monthly price
General information. The plan's terms state its price and any rise.
The full guide
Looking for the best SIM only deal? That depends on what you actually use, so it is worth knowing what to check before you switch.
What a SIM only plan gives you
A SIM card with data, calls and texts, and no handset. You keep the phone you already own, which is why these plans usually cost less than a contract that includes a device.
What to check
- Data. Most people buy more than they use. Your current bill or your phone settings will tell you what you actually get through in a month.
- Contract length. Rolling or one month plans usually give you more flexibility, while longer contracts keep you committed for longer and may be priced differently. Compare the monthly price as well as how long you are agreeing to stay. Rolling plans can be left with a month’s notice; a 12- or 24-month plan ties you in for the term, and leaving early usually means an exit fee. 30-day rolling plans explains what rolling means for the price.
- Price changes. Some contracts include a stated price increase during the term. Check the starting monthly price and any future price shown before you commit. Wisemium displays future price steps where the provider has supplied them.
- Coverage. Smaller providers run on one of the four main networks. What matters is the network underneath, and whether it works where you live and work.
Cheap is not the same as good value
A five pound plan with 1GB is not cheaper than a ten pound plan with 50GB if you run out halfway through the month and buy more. Work out what you would pay for the data you genuinely use.
Unlimited or high-data plans
If you stream on the move, use your phone as a hotspot or work away from Wi-Fi, a plan with 100GB or more, or unlimited data, can cost less than buying extra data each month. Check the fair-use terms and any speed limit the network states before you choose. High-data and unlimited plans lists the current ones.
UK networks
EE, O2, Vodafone and Three run the four mobile networks in the UK. Smaller providers such as giffgaff, Lebara, 1pMobile and iD Mobile run on them. Wisemium lists SIM plans from a number of providers; it does not list every plan in the UK.
Common questions
Can the price of a SIM only plan rise during the contract?
It can, if the contract says so. Since 17 January 2025 Ofcom has required any rise during a contract to be set out in pounds and pence when you sign up, so check the rises shown with each plan. Some networks state that their plans have no rises at all.
Can I keep my number when I switch?
Yes. Text PAC to 65075 from your phone to get a switching code, give it to the new network, and your number moves across, usually within one working day.
How Wisemium helps
Add your current plan and Wisemium keeps its cost and renewal date on record, shows that date as needing attention before it arrives, and shows the SIM plans it lists so you can compare data, price and contract length side by side.
Wisemium may receive a commission if you take out a plan through a partner. It does not affect what you pay.
Plans you can leave with 30 days’ notice
Each rolls every 30 days. Lebara states its plans need no credit check.
50GB data
£8a monthNo upfront cost
- Virgin Media customers may be eligible for double data 50GB becomes 100GB for an eligible Virgin Media customer
Eligibility and terms
- Virgin Media customers may be eligible for double data. As stated by O2, 30 September 2026. O2 confirms eligibility; not every customer qualifies.
Opens O2’s site in a new tab.
120GB data
£12a monthNo upfront cost
- Virgin Media customers may be eligible for double data 120GB becomes 240GB for an eligible Virgin Media customer
Eligibility and terms
- Virgin Media customers may be eligible for double data. As stated by O2, 30 September 2026. O2 confirms eligibility; not every customer qualifies.
Opens O2’s site in a new tab.
250GB data
£15a monthNo upfront cost
View offerOpens O2’s site in a new tab.
30GB data
£10a month
View offerOpens Lebara’s site in a new tab.
Useful to someone you know?