Airtel - Airtel Not refunding Money

By mistake, I paid airtel bill of ***.** three times and and that time the airtel Store person said it will be refunded. Now it has been more than a month and when I mail *** they say my mail ID is not registered. Let me mention that I have this number for around *-* years now and have been using this same mail for all correspondence. Now they are saying to register the email, call ***, but we all know how helpful is calling *** is! There is no right option they provide to do this! I am frustated now after doing this for a month. I need my money back i.e. Rs ****. There is no way I could find to even register a complaint on Airtel. These companies are proactive while getting customer and then go on hibernation. There has to be some other authority to make them do their work correctly.