MOSCOW, July 31. /TASS/. Russia’s Federal Antimonopoly Service (FAS) made a decision to open a case against ‘Big Four’ mobile communication operators [MegaFon, MTS, Beeline and Tele2 - TASS] because of the prices in national roaming, deputy head of the regulator Anatoly Golomolzin said at a press conference in TASS on Monday.

"Communication operators were to present proposals on the national roaming. This was not done and FAS therefore decided to open a national roaming case against the ‘Big Four’," the official said.

The regulator will shortly prepare documents stipulating deadlines for operators to close out violations. "The final decision [on the case opening - TASS] was made this week," Golomolzin said.

FAS issued a notice to ‘Big Four’ mobile communication operators and demanded tariffs change within 14 days, the regulator said on July 17. The warning refers to complete cancellation of intra-network roaming [when a subscriber is moving from one region to another and remains in operator’s network - TASS], FAS representative Elena Zaeva told reporters. Communication tariffs for subscribers inside the operator’s network should be feasible and should not depend on subscriber’s location, she added.

FAS will open cases against communication operators in respect of intra-network roaming if notice requirements are not complied with by August 13, Golomolzin said. "There is still some time left; if there is no response [from operators], we will proceed," he said. Companies "has not responded so far," he added.