Phone and SIM price rises: work out what you will really pay

A £10-a-month SIM is not necessarily £10 for every month of the deal.

Since January 2025, any price rise written into a new consumer telecoms contract must be clear in pounds and pence before you sign up. That is a big improvement, but it does not mean mid-contract rises have been banned.

The useful number is the cost across the whole minimum term, including every scheduled rise.

What changed in January 2025?

For new consumer phone, broadband and pay-TV contracts from 17 January 2025, providers cannot use an inflation-linked rise such as “CPI plus 3.9%”. They cannot specify the rise as a percentage either.

Instead, Ofcom’s rules require a provider to tell you clearly:

• how much the monthly price will rise, in pounds and pence; and
• when that rise will happen.

The information must be prominent and transparent before you are bound by the contract. A vague note hidden several clicks away is not the standard Ofcom describes.

Contracts signed before 17 January 2025 may still contain an inflation-linked or percentage-based rise. The new rule did not rewrite contracts that already existed.

Fixed rise does not mean fixed price

You may see wording such as:

£10 a month. Increases by £1.50 each April.

The increase is predictable, which is what the new rules are designed to achieve. But the amount you pay still changes, and a long contract may contain more than one increase.

That matters because two plans with the same starting price can have different totals. It also means a plan starting just before the annual rise may spend very little time at its advertised opening price.

A worked 24-month example

Suppose an illustrative SIM starts on 1 September 2026 at £10 a month and rises by £1.50 every 1 April. Its minimum term is 24 months.

Period	Months	Monthly price	Subtotal
September 2026 to March 2027	7	£10.00	£70.00
April 2027 to March 2028	12	£11.50	£138.00
April to August 2028	5	£13.00	£65.00
Minimum-term total	24		£273.00

Multiplying the headline £10 by 24 gives £240. The real scheduled total is £273 — £33 more — and the effective average is £11.38 a month.

This example assumes clean monthly billing dates and no pro-rata adjustments. A provider’s actual terms may handle the first bill or rise date differently, so check its contract summary.

Promotions are another moving part

“£5 for the first six months” and “rises by £1.50 each April” describe two separate changes. A proper calculation needs both.

Split the deal into each period where the charge stays the same:

1. Introductory-price months.
2. Normal-price months before the annual rise.
3. Months after the first rise.
4. Months after any second rise.

Then add any upfront activation charge or other mandatory fee. The CMA’s price-transparency guidance says unavoidable charges should be included in the total price shown to customers, rather than appearing only later in the buying process.

Cashback should not be used to conceal the payment schedule. Show what leaves your account first, then explain an automatic or claim-based reward separately.

What if the rise was not in the contract?

According to Ofcom’s consumer guide, if your contract did not set out how much the price could rise and the provider increases it — or raises it by more than the contract allows — the provider must:

• give you at least 30 days’ notice before the increase takes effect; and
• from that point, give you 30 days to leave without an exit fee.

Start by checking the contract summary and the terms you received when joining. If the numbers do not match, complain to the provider and keep a copy of the notice and your original paperwork.

Do not assume every scheduled increase lets you leave for free. If a fixed pounds-and-pence rise was clearly disclosed and formed part of the deal you agreed, it is different from an unexpected or excessive increase.

Different rules apply to small-business and not-for-profit contracts, so this guide should not be used as a substitute for checking those terms.

What we check on a SIM deal

For every plan, the useful facts are:

• the opening monthly price;
• when any introductory offer ends;
• the fixed amount of each rise;
• the date or month each rise happens;
• how many rises land inside the minimum term;
• upfront and mandatory charges;
• the guaranteed minimum-term total;
• the effective monthly average; and
• what the plan becomes after the minimum term.

If a provider has not made one of those facts clear, that is not a detail to guess. The plan should be marked as needing more information until it can be verified.

A lower starting price can still cost more

Imagine Plan A starts at £8 but rises sharply twice, while Plan B stays at £10 throughout a short term. Plan A gets the more exciting headline; Plan B may have the lower total and gives you more certainty.

Data allowance matters too. Paying £2 more for 100GB is not a saving if you use 8GB. Compare plans that meet the same real need, then compare their scheduled totals.

If you decide to move

Ofcom’s text-to-switch process makes a mobile move fairly painless:

• Text PAC to 65075 to keep your number.
• Text STAC to 75075 if you want a new number.
• Text INFO to 85075 to check your contract status without starting a switch.

A PAC or STAC is valid for 30 days. When you give it to the new provider, Ofcom says the switch should be completed within one working day. Check any early termination charge before committing.

The bottom line

The January 2025 rules removed the guesswork of future inflation from new consumer contracts. They did not remove price rises.

Before calling a SIM deal cheap, add every month at the price that will actually apply. We will show both the starting figure and the guaranteed total because you deserve to know what the whole deal costs, not just what fits in the biggest type.