Airtel
Non-refund of Amounts

I had surrendered my broadband connection with Airtel. At the time of setting up the broadband connection they charged me 750/- (amount in Indian Rupees). After the termination of the connection, I had made an application that I wanted to return my Modem that I am having with me back to Airtel. So, in that case how much amount in Indian Rupees would I be refunded. They told me that I will get a refund of 750 only (amount in Indian Rupees), i.e., the exact amount that I had paid to them while the connection was being created. But now they say that the instrument charges are non-refundable. Please help me.

And this is not the first time that I am having problem with Airtel Consumer Services.