MEXICO CITY (AP) — About 30,000 workers at Mexico’s largest fixed-line telephone and internet company agreed to go back to work Friday while the government mediates a dispute over wages, pensions and benefits.

The Labor Department said that it would act as mediator and that the union and company would have 20 working days to reach an agreement.

Unionized employees went on strike Thursday at Teléfonos de Mexico, better known as Telmex. It was once a state-owned company that controlled basically all phone service in Mexico. But since its privatization in the 1990s, anti-monopoly controls have forced it to yield ground to other cellphone and internet providers.

Telmex and its subsidiaries had been known for relatively cordial relations with the national Telephone Workers union, which said its strike was the first at the company since 1985.

Telmex said Thursday the demands of its unionized employees were not consistent with “the financial viability of the company.”

Unionized employees are demanding a 7.5% wage hike, plus a 2.9% increase in benefits. That would put them just over the current inflation rate of about 8%.

The union said the company had offered increases of 4.4% in wages and 1.1% in benefits.

There were also disagreements about unfilled positions, back wages and pensions.