In a letter last week to the National Telecommunications Commission (NTC), CAT claimed that Advanced International Network (AIN) did not inform AIS's cellular-service subscribers that using the "+" sign to make international calls on their mobile phones would route the call through AIN's network and not CAT's like earlier.

CAT said this would confuse callers, because the AIS website still stated that entering the "+" sign was equivalent to using the "001" international-call service code to make the calls via CAT. If the AIS customers are not aware of the change, and if AIN's service quality is poor, they will blame it on CAT.

An AIS executive said the company did not inform customers about the matter, because the AIN service was being offered on a trial basis and that AIN was not charging the customers during the trial period.

AIN won the NTC's international-call licence and started providing the service to AIS mobile-phone subscribers on a trial basis on March 1 by dialling "005" followed by the destination number abroad. However, international calls by AIS subscribers using the "+" sign are also routed call via AIN's network.

CAT also asked the NTC to consider whether AIS, the country's largest cellular operator, was breaching NTC regulations against monopolistic practices by teaming up with its subsidiary to offer the international calling service.

Wattana Iambamrung, head of CAT's labour union, said separately that the international-call traffic of AIS subscribers via CAT's network from March 1-20 had dropped to 100,000 minutes a day from the usual 300,000 minutes a day. This translated into a loss to CAT of Bt70 million in international-call revenues during the period.

CAT was aware its international-call revenues would drop following the entry of newcomers under NTC licence, but it viewed the entry of AIS into this arena as unfair, since it could capitalise on its huge customer base of more than 20 million subscribers, Wattana said.

Wattana said CAT had submitted complaints of unfair practice against AIS to the NTC twice but that the regulator had yet to take any action. He said the state agency would submit a complaint to Prime Minister Surayud Chulanont and the Council for National Security that the NTC was failing to protect the national interest.