Emergency call operators working for BT Ireland and Conduit Global are to hold a second 12-hour strike at their call centre in Navan on 7 April.
The dispute centres on demands by staff at the Emergency Call Answering Service belonging to the Communications Workers Union for a basic wage of €11.50 per hour, equal to the living wage.
It also centres on changes to certain policies and the right to negotiate through their union.
999 operators at the Navan centre held a 12-hour stoppage in February to highlight their grievances, but said they would then give the company time to deal with their issues.
CWU official Ian McArdle acknowledged that the company had pledged to reform certain policies, and that it had established an internal employee forum, but said there had been no progress on the key issues of union recognition and the pay rise.
BT Ireland won the tender to operate the ECAS service and outsourced it to Conduit Global.
It operates from three centres in Ireland: Eastpoint in Dublin, Ballyshannon in Donegal, and Navan in Meath.
In a statement tonight, Conduit Global said it "strongly regrets the decision" to take further industrial action.
"Conduit Global's employees have represented themselves in successfully driving continuous improvement during recent rounds of consultation.
"In light of the resolution of so many concerns, it appears that the CWU is choosing to place its own interests over critical public services."
It added: "We strongly urge the CWU to recognise the positive steps that have been taken and reconsider its decision to take industrial action."
The companies have previously defended their terms and conditions of employment, and have again queried how many of their employees actually belong to the CWU.
The dispute received much publicity when it emerged that the duration of toilet breaks was limited under a company policy.
However the employers have said that that policy has been revised.