Mobile company T-Mobile UK has said that it will refund all its customers who paid for calls they did not make after receiving overcharged bills.

The company has said that the error took place because of a glitch in its billing systems and has tendered an apology to all users affected by wrong billing.

The error surfaced after some subscribers complained that they had been charged for numbers they had not called.

The problem is believed to have affected about 4% of T-Mobile’s customers.

"Some T-Mobile customers wrongly received call forwarding charges when they used their voicemail," T-Mobile said, BBC reports.

T-Mobile said that it has fixed the glitch.

"This problem has now been fixed. We’ll be fully refunding every customer affected by this, a process which has already begun. We’re really sorry and wholeheartedly apologise to any customers who have been affected by this issue," it said.