Damage to the Internal unit

The Split unit A/c bought through canteen services at Chennai is still in the warranty time (Nov. 2007) During the summer in June when we were using, it was not cooling and the technician filled the gas. Repeated call initiated further check and they wanted the unit to be checked at the service centre at Anna Nagar Chennai. Mr. Chellapandian, the service manager got both the external and internal unit to check. It took over ten days and several phone calls when we were told that there is a leak from the cooling coil which they welded. it. Away from India when I returned home, I got the service people of National( I have a Panasonic also) to clean the dust when they informed that the internal unit is damaged during the repair of the tubes in the fings and the welded portion can leak and it can later land me to shell out money for even compressor. This means there that the product is defective from the origin.Please guide me and help the retired indivitual.