Airtel text based service
Every weak deducted 20 Rs

I'm fed up i don't know from where it got subscribed & now there is no option to deactivate neither we can unsubscribe while sending sms as every week it used to be deducted 20 rs from my account without accessing neither any facility nor any downloading, i'm fed up of this they did not even provide any customer care no so that we can talk to them & have informtaion & unsubscribed the service... Please Help me regardijng the same.