i-Mobile chief operations officer Jong Diloksombat said it had been "unsuccessful" in recovering the sum. He added Thai Mobile had not paid anything since 2005.

Thai Mobile is a joint venture between TOT and CAT Telecom and has about 70,000 subscribers. It commenced service in 2003. TOT is seeking to buy CAT out of the joint venture.

i-Mobile is a subsidiary of Samart Corp. It warned Thai Mobile on May 11 it would withdraw services if the amount remained outstanding.

It postponed action after TOT sought time to resolve the impasse.

TOT acing president Colonel Natee Sukonrat said it wanted to discuss the outstanding amount with i-Mobile. He claimed some contract conditions were "unfair". He specifically disliked billing at fixed rates.

Samart said the claimed amount comprised Bt250 million for customer service fees and the remainder for billing.

Thai Mobile employed Samart in 2002 to handle customer service and billing and to distribute Thai Mobile numbers to dealers. Until the dispute, Thai Mobile had paid Samart Bt800 million.

Jong explained customer service was charged at Bt80 a subscriber a month or a minimum of Bt10 million. This contract expires in October.

Billing is charged at a flat rate of Bt1.8 billion for the life of the contract, which expires in 2009. Thai Mobile has already paid Bt600 million of that figure.

Usanee Mongkolporn

The Nation