Out-of-contract mobile phone customers could be overpaying by nearly £100 per year, according to Which?
The consumer group surveyed more than 4,000 people in October 2020 to find out what mobile customers do when their contracts end.
Around a third of mobile customers either haggled for a better deal (33%) or switched providers (35%) when their contract ended, saving an average of £60 a year on their bills.
However, Which? found some customers who negotiated with their provider saved up to £96 a year.
According to Ofcom rules introduced in February 2020, telecoms providers, including mobile providers, must issue end-of-contract notifications (ECNs) warning customers their contract is about to end to help them avoid price hikes and encourage them to shop around.
Mobile providers are also required to inform customers of the best deals they have available in end-of-contract notifications.
A fifth of customers accepted the deal offered in their notification, Which? found, protecting themselves from the worst price increases.
Of those that haggled with their provider, seven in 10 said they were offered an upgraded deal, which meant more data or minutes on their plan. This compared with just over half (55%) who were offered an upgraded deal in their ECN.
One person surveyed told Which? they complained to their provider when their ECN quoted a higher price than they were currently paying. The provider eventually offered a larger data package at a lower price, underlining the importance of haggling.
Which? has a new mobile switching service for customers to compare deals at mobilephones.which.co.uk.