Switzerland's competition watchdog has fined the country's leading mobile provider 333 million Swiss francs ($269 million; 205 million euros) for abusing its dominant position by charging other companies inflated fees to use its network.
The national competition commission, Weko, said Swisscom Mobile had breached cartel rules between April 2004 and May 2005 when it forced non-Swisscom customers to pay 0.335 francs ($0.27; 0.21 euros) a minute to call into its network.
Swisscom rejected Weko's findings and said it would seek to overturn the fine in court.
The company, the mobile-phone arm of Switzerland's former telecommunications monopoly, argued that it was being unfairly singled out and had received no warning that it might be breaching competition rules. The Swiss government is the majority shareholder in Swisscom.
Shares in Swisscom were up 0.9% at 474.25 francs ($383.79; 292.14 euros) on the Zurich exchange by midmorning.