voltas ac 1.5 ton - Voltas service center not responding after the technician sent by their service center did an incomp

The AC in context we purchased in May, ****. I had asked for routine annual service at Voltas authorized service center last Saturday because *. to do a routine deep clean-up and *. the cooling was not adequetly happening. The service person came and after inspecting the AC said that the AC needed to be refilled with GAS. We were surprised as we purchased the *.* ton Window AC only in May, ****. He suggested there could be a micro leak which is leaking the GAS.The service person started to fill in the GAS in the AC without taking our consent and showing us through a meter how much gas was left. He charged us Rs.****/- and Rs. ***/- for his service and left after switching the machine on at ** degrees. But even after an hour of running, we found the cooling condition has not improved, on the contrary it has worsened. We again called both the service center and the service man and stated the problem. The technician promised to revisit us on sunday at ** AM and did not turn up. Now since Sunday(*/*) and today (**/*) we are unable to contact the service center numbers and the technician's number as neither one is picking the call. I want Voltas service center to send a technician to detect the problem, whether it is a case of Manufacturing problem(s) or Micro leak. Now as we cannot contact anybody we feel helpless and feel that we are probably being cheated.