The British operator failed to bill departing customers accurately.
The British regulator Ofcom has found that O2, Telefonica’s UK business, overcharged more than 140,000 customers who left O2 between 2011 and 2019.
Ofcom has fined O2 £10.5 million for the overcharges which were due to billing errors which charged some people twice when the final bill was calculated.
Ofcom opened an investigation into potential issues with the way O2 was billing customers who were leaving the provider in 2019.
In total, more than 250,000 customers were billed incorrectly, amounting to £40.7 million. About 140,000 customers paid them, which added to up £2.4 million.
O2 had identified issues with its billing processes in 2011, but efforts to address them did not succeed and overcharging continued.
O2 has accepted the findings of Ofcom’s investigation and refunded the customers affected plus 4%.
The operator will donate to charity the amount it overcharged customers it cannot reach. O2 has also fixed its billing system.