O2 Ireland has scrapped roaming charges between the Republic of Ireland and Northern Ireland for all of its 1.6 million customers.
O2 has also abolished roaming charges across Great Britain and Ireland for its business customers. The changes will be effective from April.
"Our customers have told us that it makes no sense to pay roaming charges while making calls on the island of Ireland. This is particularly important to our customers who live and work near the border, many of whom have had to endure inadvertent roaming charges," said Danuta Gray, chief executive of O2 Ireland.
"The elimination of roaming charges across Great Britain and Ireland will help many of our business customers to improve their competitiveness and to be more successful", continued Ms Gray.
The business sector welcomed today's announcement by O2.
"Inadvertent roaming charges have been an issue for members of Chambers Ireland affiliated chambers on both parts of the island. This action will be particularly beneficial for companies based in the border region, " said Chambers Ireland chief executive, John Dunne.
"Furthermore, given that the UK is still the Republic's biggest market for both exports and imports, the abolition of roaming charges throughout the UK for business customers is also to be welcomed as a means of facilitating business in its efforts to win more sales in this crucial market for Ireland" he added.
Minister for Foreign Affairs Dermot Ahern, who has raised the need for an all-island telecommunications market with British officials and backed calls for other operators to end roaming charges, said: "As it stands only Southern companies and mobile phone users stand to benefit from these moves.
"It is imperative now that O2 UK move now to replicate the move by O2 Ireland, and that other Northern telecom operators follow suit."