Ringing up the charges: Unjust mid-contract price hikes could leave mobile customers £120 out of pocket, Which? warns

Mobile customers on Sim-only contracts could be charged up to £120 more than they expected over the course of their contract due to two years of eye-watering price hikes, Which? warns, as the consumer champion campaigns for an end to unpredictable mid-contract price rises in the telecoms industry. 

Which? is sounding the alarm on unpredictable mid-contract price hikes as it campaigns for providers to do the right thing and stop these increases – and for Ofcom to ban the practice altogether.

The Big Four mobile firms – EE, O2, Three, Vodafone – represent 68 per cent of the UK mobile network market and hike prices every April in line with the Consumer Price Index (CPI) or the Retail Price Index (RPI) plus an additional 3.9 percent, with no detailed breakdown of how that additional figure is calculated. If Sim-only customers are in-contract and want to avoid these hikes, they can be charged punitive exit fees of up to almost £300 to leave their contract early.

Some smaller networks, including BT Mobile, iD Mobile, Talkmobile and Tesco Mobile, will also hike their prices in line with CPI plus 3.9 per cent in April 2024.

However, these unpredictable mid-contract price hikes particularly add insult to injury for loyal Big Four mobile customers – who are already paying significantly more for their Sim plan than they would at smaller rival networks.

Based on snapshot analysis of pricing data and Bank of England inflation forecasts, Which? has predicted how much EE, O2, Three, Vodafone Sim-only customers could see their bills increase by in 2024 and over the course of their contract, compared to the amount they were quoted when they originally signed up.

On average, EE, Three and Vodafone customers could see increases of more than 8 per cent in 2024 while O2 customers could see rises of over 10 per cent.

Based on prices on the providers’ websites for a 12-month Sim-only contract with unlimited data, calls and texts, O2 and EE customers could see the biggest annual increases of £24.02 and £20.58 respectively in the year from April 2024. Three customers could see a smaller annual price hike of £15.88 on average.

These hikes would come on top of the eye-watering price hikes of more than 17 per cent many consumers faced in 2023.

Which? also calculated how much extra these two rounds of price hikes could cost a customer for each provider who took out a deal in November 2022 over the course of a 24-month Sim-only contract with unlimited data, calls and texts.

Based on snapshot pricing analysis, O2 customers could see the biggest potential price hike of up to £124.21. O2 is the only mobile network that uses RPI – which is typically higher than CPI and has been criticised as an inaccurate measure of inflation by the Office for National Statistics – to calculate price changes.

EE customers could face the next highest potential price hikes of up to £102.17. Three and Vodafone customers could face smaller price hikes of up to £87.57 and £80.27 respectively.

Even on a lower data contract, these price hikes are still significant. Which?’s snapshot pricing analysis found that for a 24-month Sim-only contract with at least 8GB data, consumers could face price hikes of up to £76.62.

These price hikes feel especially unfair when Big Four customers could be paying significantly less elsewhere if they were able to move from their contracts without paying additional exit fees.

For example, an unlimited data 24-month contract with a Big Four provider costs from £22 to £28 per month – before mid-contract price hikes – but equivalent rolling contracts with unlimited data are available for as little as £18 per month at rival networks. These contracts also offer the flexibility to switch if prices rise. Which? analysis shows that by switching away to a rival provider, Big Four customers could save as much as £120 a year, even before the upcoming price hikes are taken into account.

Which? believes it is unfair for consumers to have to commit to deals with unpredictable prices, meaning they do not know how much they can expect to pay over the course of their contract when they sign up. This is why the consumer champion has launched its ‘The Right to Connect’ campaign calling for an end to unpredictable mid-contract price hikes.

Ofcom is currently reviewing inflation-linked, mid-contract price rises amid concerns that they do not give consumers sufficient certainty and clarity about what they can expect to pay. It is due to publish its consultation on this issue in December.

Which? is calling on all providers to do the right thing and stop this practice ahead of Ofcom’s final decision, to ensure that customers are not impacted by similar unpredictable price rises next April.

In the longer-term, the consumer champion believes the regulator should ban these unpredictable mid-contract price hikes as they unfairly penalise consumers, make it hard for people to predict how much their telecoms contract will cost and dampen price competition in the market.

Rocio Concha, Which? Director of Policy and Advocacy, said: 

“A good broadband and mobile connection is essential to modern life. It’s completely unacceptable that these unpredictable mid-contract price hikes have been allowed to continue in the telecoms industry for so long. These contract terms dump the burden of managing inflation risk onto customers, obfuscate prices and undermine competition.

“Which? is calling on all providers to do the right thing and cancel 2024’s above inflation price hikes. Ofcom should also use their review to finally ban these unjust mid-contract price hikes that harm consumers and undermine competition. Consumers need to know exactly how much their contract will cost when they sign up.”


Notes to editors

Which? ‘The Right to Connect’ campaign 

Access to the internet has become a basic necessity to life in the 21st century – for everything from work and school to socialising, shopping, banking, and accessing essential government services.

Which?’s ‘The Right to Connect’ campaign is calling for clearer and fairer pricing for telecoms customers, because when it comes to basic necessities like a reliable mobile or internet connection, consumers deserve clarity. Read more about the campaign here.


Which?’s calculations are based on a snapshot analysis of data from mobile network websites (for 12 month Sim-only contracts) taken in October 2023, and industry database information for prices in November 2022 (for 24 month Sim-only contracts). This forecasting is based on a hypothetical customer paying these amounts when the March 31/April 1 price rises were instituted in 2023.

The estimate of CPI at 4.5% in January 2024 is a mid-estimate based on the Bank of England inflation quarterly forecasts in the August MPC Report (4.9% in Q4 2023 and 4.3% in Q1 2024). The Bank of England does not routinely forecast RPI inflation. Instead, the estimate of RPI at 6.5% is based on the percentage point differences between CPI and RPI over the past year according to the ONS inflation tables released monthly. This difference is also reflective of the average of external forecasts tracked by The Treasury.

Table 1: April 2024 price rise on a 12 month unlimited data Sim-only contract


Price rise policy

Projected price rise in 2024

£ difference per year after projected April 2024 price rise based on Unlimited data Sim

EE Mobile

CPI + 3.9%



O2 Mobile

RPI + 3.9%




CPI + 3.9%




CPI + 3.9%



Prices for 12 month contracts, unlimited data, calls and texts, no limits on speed, prices taken from provider websites on 17th October 2023.

Table 2: April 2023 and 2024 price rise on a 24 month unlimited data Sim-only contract





Contract length (months)





Original cost of contract





Cost of contract with 2023 and 2024 price rises factored in





Potential difference over full contract





Prices from industry database, deals starting 4th November 2022. Prices for 24 month contracts, unlimited data, calls and texts, 

Table 3: April 2023 and 2024 price rise on a 24 month 8GB or more data Sim-only contract





Contract details

24 months, 25GB

24 months, 20GB

24 months, 8GB

24 months, 150GB

Original cost of contract





Cost of contract with 2023 and 2024 price rises factored in





Potential difference over full contract





Prices from an industry database, deals starting from Nov 4 2022. Prices for 24 month contracts, cheapest contract with at least 8GB data, unlimited calls and texts, 

Potential exit fees facing customers were calculated using providers’ terms and conditions and Which? analysis of pricing data. See these calculations in our press release from February 2023: https://press.which.co.uk/whichpressreleases/mobile-customers-stuck-in-catch-22-between-mid-contract-price-hikes-and-exit-fees-of-over-400-which-warns/

Right of replies

A spokesperson for EE said: ‘We understand that price rises are never wanted nor welcomed but recognise them as a necessary thing to do given the rising costs our business faces.

‘Our price rises are annual, contracted and transparent and we make this clear when customers sign up or renew their contract. With the average price increase just above £1 per week, and 2 million pay as you go customers were excluded from price changes in 2023 – we’re also doing all we can to ensure our services are accessible to the widest group of customers possible through our market leading social tariffs.’

A spokesperson for O2 said: ‘We are always clear and transparent with customers about any future price increases, which are re-invested back into our network to meet significantly increased demand for our services.

‘While we know that price changes are never welcome, this year bills increased by an average of 10.0%, or less than 10 pence per day, which is below inflation and reflects the fantastic value we provide for fast and reliable connectivity that is used almost constantly.’

Three provided clarifying information, but declined to provide a wider comment.

A spokesperson for Vodafone said: ‘It’s too early to make any comments on next year’s figures. We will continue to ensure customers registered as financially vulnerable can stay connected by offering social mobile and fixed tariffs – these are not affected by any price increases.’

About Which?

Which? is the UK’s consumer champion, here to make life simpler, fairer and safer for everyone. Our research gets to the heart of consumer issues, our advice is impartial, and our rigorous product tests lead to expert recommendations. We’re the independent consumer voice that influences politicians and lawmakers, investigates, holds businesses to account and makes change happen. As an organisation we’re not for profit and all for making consumers more powerful.

The information in this press release is for editorial use by journalists and media outlets only. Any business seeking to reproduce information in this release should contact the Which? Endorsement Scheme team at endorsementscheme@which.co.uk.

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