Airtel Prepaid — Unwanted subscription of tunes

Address:

North 24 Parganas, West Bengal

I've an Airtel prepaid connection for last 4 years, not only me, my parents also have Airtel prepaid connection. From last 6 months or so, we're facing an irritating problem. Sometimes an incoming call comes to our cells and as soon we receive the call, some tunes are subscribed to our connection and immediately our exisiting balance got deducted. This is really very cheap approach from an organisation like Airtel...some steps against them should be taken immediately...such kind of promotion isn't acceptable at all.