Mobile phone operator O2 Ireland has admitted overcharging a further 71,000 customers following a review of its systems.
The disclosure means that 136,535 O2 subscribers - more than 10 per cent of its customer base - were overcharged since February 2004.
O2 said it had repaid €721,892 to affected customers and had agreed to a request by the Commission for Communication (ComReg) to allow outside consultants to review and monitor its billing system processes.
The mobile company initially admitted to The Irish Times last month it had overcharged 65,000 customers for roaming calls received while abroad. But the additional overcharging, which affected another 71,000 users relates to different calls charges.
The new admission by O2 was contained in a report on the overcharging by ComReg, which said the regulator was "clearly disappointed that internal billing and management controls" had failed to safeguard mobile customers.
The report also reviewed Vodafone's recent admission that it had overcharged 22,436 customers for roaming calls made while users travelled overseas.
ComReg said Vodafone had reported that it had overcharged its these mobile users by €147,739.
Both Vodafone and O2 have agreed to pay an additional credit to all of the customers who had actually overpaid on their bills.
O2 said yesterday this "inconvenience" payment would cost it about €320,000 and Vodafone said it would cost about €80,000.
Mr John Doherty, chairman of ComReg, said these extra payments would seek to recognise the anger that customers felt about being overcharged.
"It is, however, imperative that trust in the accuracy of billing systems is restored. While in many cases, the individual amounts involved were relatively small, nevertheless, the circumstances involved were serious," he said.
ComReg said it would continue to monitor developments and would intervene again, if necessary, to protect consumers.
Dr Matt Lucas, a telecoms expert with the US firm Telestrategies, said inaccurate billing had plagued the industry since its inception and overcharging incidents were very common.
Meanwhile, Esat BT said yesterday it had sent 1,900 bills to a group of former customers in error. The firm said no customers had paid any of the bills and no money changed hands.
