BT has incorrectly charged some of its broadband customers for exceeding their usage cap in June.
According to MoneySavingExpert.com, the issue occurred between June 22nd and 23rd and affected people with a limited broadband package.
The exact number of people who were accidentally charged too much has not been disclosed.
However, BT has confirmed that these customers will be automatically refunded.
A spokesperson said: "BT is writing to a small number of broadband customers to apologise for a mistake which meant they were wrongly charged for going over their usage limit in June.
"All of these customers will be refunded for the amount we overcharged without them having to do anything."
BT added that the problem arose following a "glitch in our systems", which meant that some people were inadvertently charged "a few pounds too much".
This comes a month after BT broadband customers experienced two service outages in two days.