The leading mobile phone carrier and mobile network operator of the United Kingdom T-Mobile has reportedly apologised to thousands of its customers for an error that left them charged for phone calls that were not made by them.

It is believed that 4 per cent of the customers of T-Mobile have been affected by the issue. It is understood that the mobile phone carrier will be fully refunding those customers.

Meanwhile, T-Mobile has blamed an error in their billing systems for triggerring off the issue.

The problem was brought to light first by Bitter Wallet, a consumer website, according to the estimation of which the issue could have affected around half a million T-Mobile's mobile phone customers.

According to T-Mobile, some of its customers had wrongly recieved charges related to call fowarding when they had used the voice mail services. This according to the carrier was due to a technical error.

T-Mobile nevertheless said that they have fixed the problem besides deciding to refund every affected customer of theirs.