I have been with airtel for two years and I have seen the services go from bad to the worst... The service centres talk as if they are doing you a favour talking to you. Also, the internet is so bad that once the FUP is used, it looks like you are using dial-up connection.
Also, to disconnect the connection they will keep calling you till you get more irritated. Same thing happened to me. They kept calling me everyday for one month, even if you answer or do not answer the call.
High charges for nothing that will be useful for you...