Customers of the Everything Everywhere phone network - which includes the Orange and T-Mobile brands - have been warned that their services may be limited for a short time in the New Year as the company carries out a £25m upgrade of services.
Phone and data services could be lost for between 12 and 48 hours as work is carried out to expand 3G services to 94% of the Northern Ireland population by April 2013.
The work will take place on a mast-by-mast basis between January and March.
EE has given assurances that the work will be put on hold to allow full services on Christmas Day, Boxing Day and New Year's Day.
As well as the upgrade works on the existing 2G and 3G network in Northern Ireland, EE is also launching superfast 4G mobile services on Christmas Day.
Despite being notorious for being the worst area in the UK for phone and data coverage, network team chief executive Scott McGimpsey said when the upgrade completes in April 2013, consumers and businesses here will have access to one of the best performing mobile networks in Europe.
"While people will lose services temporarily in the New Year to allow for expansion of the 3G network, the long-term benefits will be massive," he said.
"And with 4G being launched in the greater Belfast area on Christmas Day, customers in the greater Belfast area will be able to avail of some of the fastest mobile internet in the UK.
"We are currently operating at least three to four months ahead of our competitors in delivering these services and we have invested heavily in expanding services in Northern Ireland, which was traditionally a poorly -served area compared to the rest of the UK."
Enterprise Minister Arlene Foster added that the launch of 4G services in Belfast is positive news for Northern Ireland.
Vodafone, BT, O2 parent Telefonica, Hutchison 3G, EE, Hong Kong conglomerate PCCW and UK network supplier MLL Telecom will compete in next year's 4G auction in what marks the largest ever sale of mobile airwaves in the UK.
Regulator Ofcom said the auction, which kicks off in January, will herald "better, faster and more reliable mobile broadband connections" for consumers across the UK.
Ed Richards, chief executive of Ofcom, said: "The 4G auction will be a competitive process that will dictate the shape of the UK mobile phone market for the next decade and beyond."