Thai fixed line operator TOT has filed two lawsuits demanding unpaid network access charges from its sister state-run telco CAT Telecom and its two cellular concessionaires, DTAC and True Move, amounting to THB15 billion (USD500 million) including interest, reports the Bangkok Post. In one case, TOT named CAT Telecom as the first defendant and DTAC as the second, demanding unpaid access charges plus 1.25% interest totalling THB11 billion. The second case, against CAT Telecom and True Move, seeks THB4 billion in access fees and interest. DTAC and True Move, which offer GSM services under Build-Transfer-Operate (BTO) concessions with CAT, stopped paying access charges to TOT in November last year, in favour of the new interconnection charge framework introduced by the National Telecommunications Commission. CAT is responsible for collecting charges from the two cellcos for interconnecting with TOT’s PSTN. Another CAT concessionaire, Digital Phone, a subsidiary of the country’s leading cellco Advanced Info Service (which operates under a BTO contract with TOT), also stopped paying access charges to TOT in June. However, TOT said that Digital Phone subsequently relented and paid THB72 million last week. According to the Bangkok Post, TOT earned THB14 billion from access charges last year.