UK mobile phone company EE has been fined £2.7m by regulator Ofcom for overcharging tens of thousands of customers.
EE is owned by telecoms giant BT, which acquired the mobile operator last year in a £12.5 billion deal.
EE customers who called the company's 150 customer services number while roaming within the EU were incorrectly charged as if they had called the US.
Ofcom said the mistake saw customers charged £1.20 per minute, instead of 19 pence per minute.
As a result, at least 32,145 customers were overcharged around £245,700 in total.
It added that EE wrongly decided it could not identify the people it overcharged and was proposing to give their money to charity, which would have left them out of pocket.
In another breach, despite making it free to call or text the 150 number from within the EU from November 18 2015, EE continued to bill 7,674 customers up until January 11 2016.
In total, these customers were overcharged £2,203.33, although in this instance EE issued full refunds to those affected.
Proceeds of the fine will be passed on to the UK Treasury.
Ofcom said the penalty reflects a 10% reduction in light of EE's agreement to enter into a formal settlement and its admission of full responsibility for the breaches.
While the majority of customers have now been refunded, EE was unable to identify at least 6,905 customers, who have been left around £60,000 out of pocket.
The company has made a donation of just under £62,000 to charity in lieu of the payments owed to these customers.
However, Ofcom is requiring EE to make further attempts to trace and refund every customer who was overcharged.
