New Eircell customers have to wait up to 10 days to have applications for mobile phones processed because of a dispute involving 70 members of the Civil and Public Service Union.
Existing customers are also having difficulty having queries and requests for service processed.
The union is objecting to the hiring of new staff at rates of pay about £2,000 below that of existing staff. According to the union the new recruits' starting salary is £8,000 a year.
A spokesman for Telecom Eireann said the company was not prepared to compromise on the new measures, which were being taken to improve customer services.