Bluestar - Ac not repaired

Last month in the month of may my ac was not cooling properly,I call the services centre people they got it fixed and charged rs.**** from me.again my ac is facing the same problem again when I called the service centre people they said they will Send the technician but they didn’t.they said they will send the technician within ** hours but after ** hours also the technician have not come.i called them again but again they said they will send the technician but the technician have not come till now.when I asked them about the charges they said the technician will tell us.why should I pay twice for the same problem..should I pay every month to them.they did not fixed the problem properly. This blue star people have cheated. My personal detail are -Amrita Raj c-*** Harina colony dhanbad