Johannesburg- Operations were stable at Sentech following strike action by members of the Communication Workers Union (CWU), the company said.
"The company continues to concentrate its remaining capacity on minimising the impact on customers," spokesperson Sithembele Senti said.
Union members were demanding a 10% wage increase for the lowest paid, 9% for middle-income earners, and 7% increase for the highest paid staff.
They also wanted a guaranteed 13th cheque in the current financial year.
Alternatively, members would settle for 11% increase and a 13th cheque in a 2015/16 agreement.
Other demands were a housing allowance of R1 450 and a moratorium on retrenchments during the wage agreement period.
"These demands by CWU are not affordable and will have a negative effect on the sustainability of the business.
"Sentech remains open and agreeable to further engagements with the union in order to resolve the current dispute and will keep all its stakeholders and media updated on developments on regular basis," Senti said.
Earlier CWU general secretary Thabo Mogalane said the strike began this week, affecting operations in Johannesburg, Durban and Cape Town.