Spain’s antitrust regulator, the National Commission Competition (CNC) has taken disciplinary action against Telefónica, Vodafone and Orange, accusing the operators of abusing their dominant positions.

CNC has opened legal proceedings against the operators after a complaint was filed by UK carrier the BT Group. The complainant claims that the operators have been squeezing out the profit margins of virtual mobile operators, which don’t own their own network.

“The complaint alleges that the operators have committed an abuse of their dominant positions,  individually or collectively, by consistently narrowing the operating margins for MVNOs when setting prices for wholesale services  origination and call termination in their national telephone networks  mobile, and retail prices for mobile call services, especially in the business segment,” CNC said in a statement.

The regulator added that the probe must be closed within 18 months.