Tens of thousands of subscribers to Smart Telecom - a firm supplying broad-band and fixed line services - will have services restored within three days.
An interim deal brokered by ComReg will see customers able to make local and national calls, as well as receive calls.
Smart Telecom buys Eircom services wholesale and then sells them on to users.
Yesterday many Smart Telecom subscribers had their services severely curtailed without warning.
Eircom says it has issued warnings to Smart for failure to pay on nineteen occasions.
After hours of talks involving Smart Telecom, Eircom, and Comreg, an interim agreement was finally hammered out.
ComReg says the arrangements will enable customers to select any telephone provider of their choice for the long term.
The regulator acknowledged Eircom's co-operation for putting in place the measures.
However, the deal does not address the issue of Smart Telecom's debts to Eircom, which Eircom says stand at €4 million, of which over €1.5 million is in arrears.
Smart Telecom service provider employs 430 people at several locations across the country. The future for those workers now looks bleak.
The company has been in the process of restructuring, and recently announced around 150 job cuts and plans to sell off some of its business.
