Eircom has said that up to 100,000 customers who were accidentally overcharged will be refunded.
The company said that because of a software problem callers were charged for calls that did not get through.
The problem came to light when it emerged that Eircom had charged some callers to RTÉ One's Late Late Show competition line even though they did not get through.
Customers on 500,000 calls were overcharged between 24 April and 17 May.
Yesterday the company announced it is cutting 900 jobs by 2010, starting with 400 job cuts by the end of this year.
