Millions of UK consumers might be compensated following the filing of a court action against mobile phone networks.
Consumer advocate Justin Gutmann claims that Vodafone, EE, Three, and O2 overcharged people for phones that were no longer under contract.
He is suing for more than £3 billion in damages on behalf of 4.8 million individuals.
EE responded by calling the report "speculative," while O2 stated that it had not been approached.
Vodafone stated that it did not have enough information for its legal experts to evaluate, while Three declined to comment.
The "Loyalty Penalty Claim" is being filed with the Competition Appeal Tribunal on behalf of customers who purchased contracts that included a mobile phone and services such as data, call minutes, and SMS.
Gutmann, a former Citizens Advice official, thinks that 28.2 million UK mobile phone contracts might be impacted beginning in 2007.
If the lawsuit is successful, he estimates that someone with contracts with only one of the cell companies might get more than £1,800.
Gutmann stated that when the contracts were first agreed upon, the cost of repayment for the contract's minimum duration, which is normally 24 months, covered both the cost of the mobile and the usage of services.
He said that even though users had previously paid for their mobile devices, the UK's four largest network providers and their parent corporations did not cut the amount they charged customers once their minimum contract period expired.
According to him, this meant that existing customers were being taxed for something they had already paid for and were being charged more than a new client on deals like Sim-only packages.
"If our claim is successful, it will finally stop these firms from taking advantage of their loyal customers and stop the immoral practice of loyalty penalties," Gutmann stated.