Airtel — Not refunding the money

I am from Silvassa, my Mobile no. was [protected]. I have bought Airtel card and used the service for 1 month. As I suffers from the heavy loaded bill amount, suddenly I stopped the service. According the customer care, I paid extra money. As they ensure me that to return it back within 15 days. I have to collect 407.0/- from them. Also they send the extra bill to me even I stopped the service. Still i have not received the money from them for 2 months. Whenever I visit to the Airtel office in Silvassa, they are not giving me confirmation about the money refund and refusing me to tell the status. They are just telling me to wait for 45 days.