AC is not giving proper cooling

Location/place: Chennai-Tamilnadu

Name of company/service: Videocon

Dear Sir,
I brought two AC-VIC-1.5TN-VYS536 L1-18 kgs on July 27, 09 from Tambram branch of Next. One Ac is working perfectly all right but the another AC is not cooling properly right from its installation. I complaint but technician is not listening. Please get it repaired.