Cheapest Mobile Phone Deals UK 2026 — SIM Only & Contract Compared

If you already own a handset you are happy with, a SIM-only deal is the single fastest way to cut your mobile bill. You are not paying off a phone in monthly instalments, so the price you see is purely for minutes, texts and data.

SIM-only plans come on either 30-day rolling contracts (cancel any time) or 12-month contracts (slightly cheaper per month). The 30-day option gives you flexibility; the 12-month option locks in a rate before any mid-contract price rises kick in.

Most networks now include unlimited UK minutes and texts as standard, even on their cheapest plans. The main differentiator is data allowance — and prices have dropped sharply thanks to competition from MVNOs (mobile virtual network operators) such as Giffgaff, Smarty, Lebara and Voxi.

Below is a snapshot of the cheapest SIM-only plans available right now, grouped by data tier. Prices change frequently, but these represent the best value at the time of writing.

Prices checked July 2026. Introductory offers may apply for limited periods.

The sweet spot for most users is the 30 GB tier. Ofcom data shows the average UK smartphone user consumes around 6.4 GB per month, so 30 GB gives you plenty of headroom for streaming, navigation and the occasional hotspot session — all for around £10 per month.

The four big UK mobile networks — EE, Three, Vodafone and O2 — own the physical masts and infrastructure. Everyone else (Giffgaff, Smarty, Lebara, Voxi, Tesco Mobile, Sky Mobile, iD Mobile) is an MVNO: a mobile virtual network operator that rents capacity from one of the big four.

Which network does each MVNO use?

• Giffgaff & Tesco Mobile: O2 network
• Smarty: Three network
• Voxi: Vodafone network
• Lebara: Vodafone network
• Sky Mobile: O2 network
• iD Mobile: Three network

In practice, an MVNO gives you identical coverage to the parent network because your calls and data travel through the same masts. The main trade-off is that MVNOs sometimes have slightly lower data priority during peak congestion, although most users never notice a difference.

Why are MVNOs cheaper?

MVNOs have lower overheads — no shops on the high street, minimal advertising budgets, and lean customer-service teams (often app-based or community-driven). Those savings get passed directly to you. Giffgaff, for example, relies on a community forum for most support queries, which keeps operating costs extremely low.

If you get good signal from a particular network in your area, there is very little reason not to use the cheaper MVNO that runs on it.

If you need a new phone, a contract deal bundles the handset cost and airtime into one monthly payment, typically over 24 or 36 months. While the headline monthly price looks higher than SIM-only, you are effectively getting an interest-free (or low-interest) loan for the device.

How to tell if a contract is good value

1. Check the total cost of ownership. Multiply the monthly payment by the contract length and add any upfront cost. Compare that total against buying the phone outright plus a cheap SIM-only deal.
2. Look at the airtime element. Many contracts separate the handset repayment from the airtime cost. If the airtime portion alone costs more than an equivalent SIM-only plan, you are overpaying.
3. Factor in mid-contract price rises. Most networks increase your bill by CPI + 3.9% each April. On a 36-month contract, that can add £3–£5 per month by the final year.

Tip: split the deal

Consider buying your handset separately — refurbished or on a 0% credit card — and pairing it with a cheap SIM-only plan. This approach almost always works out cheaper over 24 months, and you keep the flexibility to switch networks whenever you like.

Since 2023, most UK mobile networks have included a clause in their contracts allowing them to raise your bill once a year, typically in March or April. The standard formula is:

Your bill increase = CPI inflation rate + 3.9%

With CPI running at around 2.5% in early 2026, that means a typical increase of roughly 6.4%. On a £40 per month contract, that adds £2.56 per month — or £30.72 extra over a year.

Which networks apply mid-contract rises?

• EE, Vodafone, Three: CPI + 3.9% annually
• O2: CPI + 3.9% annually (introduced 2024)
• Giffgaff: No mid-contract rises (rolling monthly)
• Smarty: No mid-contract rises (rolling monthly)
• Lebara: No mid-contract rises (rolling monthly)

This is one of the strongest arguments for rolling 30-day SIM-only deals: your price never goes up mid-contract, because there is no contract to be mid-way through. If a network raises its standard pricing, you simply switch to a cheaper competitor next month.

Switching your mobile network in the UK has been straightforward since Ofcom overhauled the process in 2019. Here is exactly how to do it:

Step-by-step switching process

1. Choose your new deal. Pick your new SIM-only or contract plan from any network or MVNO.
2. Request your PAC code. Text PAC to 65075 from the phone number you want to transfer. Your current network must reply within 60 seconds with your PAC (Porting Authorisation Code) and any early termination fees.
3. Give your PAC to your new network. When you sign up for your new deal, enter the PAC code. Your new network handles everything from here.
4. Your number transfers within one working day. There will be a brief period (usually a few hours) when your old SIM stops working and your new SIM activates. This typically happens in the morning.

What if you do not want to keep your number?

If you are happy to get a new number, text STAC to 65075 instead. This gives you a Service Termination Authorisation Code, which simply ends your old contract without porting your number.

Can you switch if you are still in contract?

Yes, but you may have to pay an early termination fee (ETF). This is usually the remaining monthly payments on your contract, minus the cost of your data allowance. Your network will tell you the exact fee when you request your PAC. If the fee is high, it may be worth waiting until your contract end date — you can check this by texting INFO to 85075.

When your initial contract term expires, most networks will automatically roll you onto a 30-day plan at the same price (minus any handset repayment element, if the contract separated that out). However, some networks keep charging you the full amount — including the handset repayment portion — even though you have already paid off the phone.

Check your end date and act

Text INFO to 85075 to find out exactly when your contract ends. Set a reminder a month before, and start comparing deals. The best time to shop around is in the final 30 days of your contract, when you have maximum leverage:

• Your current network will offer you a retention deal — often cheaper than their advertised prices. Call and negotiate.
• Rival networks offer switching incentives — cashback, bonus data, or discounted first months.
• You can switch without any penalties once you are out of contract.

Whatever you do, do not stay on a rolled-over contract without checking the price. If you have finished paying off your handset, you could be overpaying by £15–£25 per month for absolutely nothing.