CAT complained in a letter to the National Telecommunications Commission (NTC) last week that AIN failed to inform AIS's mobile-phone subscribers that if they used the "+" symbol to make international calls, their calls would be routed through AIN's network rather than through CAT's as usual.

CAT claimed this would confuse callers, because the AIS website still advised that entering the "+" symbol was equal to entering the 001 international calling code to make calls via CAT Telecom.

If AIS customers were unaware of the change, and AIN's service quality was poor, they would blame CAT.

AIS president Wichian Mektrakarn said his company sent a short message to its customers informing them of the trial of the international calling service. However, it did not contact all 20 million customers.

AIN tested its service between March 1 and March 15 and charged customers who made calls. Having been granted an international-call business licence by the NTC, AIN plans to offer commercial service with the 005 prefix later this year.

Wichian said AIN collected fees from customers who made international calls during its testing period whether they dialled "+" or 005. Fees from customers who made calls without being informed they were part of a test will now be transferred to CAT Telecom.

"We finished the trial period on March 15. Our customers who use the '+' symbol will be diverted to CAT's network as usual. However, when AIN kicks off its commercial service, we'll use the same 'plus' sign once again" Wichian said.

He added that whether the international calling traffic of AIS customers was routed to CAT or AIN, CAT still gained revenues, because AIN leased CAT's international gateway to connect international calls.

Sirivish Toomgum

The Nation