Mexico's No. 1 fixed-line operator said Wednesday that a competitor must pay a debt of 1.8 billion pesos ($154 million) after its attempt to appeal the payment was struck down in court.

Telmex, owned by Mexican magnate Carlos Slim, said the firm Marcatel must pay a debt dating back to February 2008 after a court rejected its final appeal.

The fixed-line giant accuses Marcatel of not paying the full amount owed for connecting to the network of Telefonos del Noreste, a Telmex subsidiary.

By law, the fees for connecting to Telmex's vast network are negotiated bilaterally between Slim's company and its competitors, although the latter frequently complain that they are exorbitant.

Telmex accuses Marcatel of unilaterally establishing its own interconnection fees in 2008 and ignoring contractual agreements.

According to Telmex, which has 12.5 million fixed-line customers in Mexico, it "never stopped providing interconnection services to Marcatel" during the court battle.