There are an estimated 76,000 customers who may be due refunds
Eircom has been hit with a 2.45 million euro penalty for overcharging customers.
The company, now known as Eir, will refund customers and also make changes to its billing practices.
The Commission for Communications Regulation took enforcement action against Eircom and says the company has committed to paying a 2.45 million euro penalty.
Eir's also implementing a series of 'backward looking measures' , where it will identify customers who were incorrectly overcharged historically and have not been refunded.
There are an estimated 76,000 customers who may be due refunds, valued at 6.7 million euro.
The focus will be on customers incorrectly charged due to a broken bundle on the customer's account and where customers were charged after requesting the end to their service.
It'll also look at those who faced early cease charges when they were allowed to cancel without payment.
The company will appoint and Independent Auditor to review the effectiveness and implementation of the measures.

Closure On Section Of M6 Due To Fire On Lands Adjacent To Carriageway
Phased Social Media Age Restriction Being Proposed By European Commission In September
Boyfriend Of Murdered American Jamey Carney Detained In Jordan
Intel To Invest €5BN In Leixlip Campus
Households Asked To Conserve Water As Heatwave Continues
Public Order And Assault Cases Rise By 11% in Two Years
Man In His 40s Dies After Hit-And-Run In Kildare
HSE Say Some Records Accessed During Cyber Attacks