Airtel — auto deducting amount for whatsmob services

Address:

Ernakulam, Kerala, 682020

I recharged for an amount of 250₹ and my account was deducted by 150/- for Whatsmob services that I did not even ask for ! The same had happened once before, an amount of 75/- was deducted earlier. I deactivated the service but I want a refund of the amount that was deducted from we for a service that I did not even use ! Why can't u ask the customer before deducting amount from their accounts?? What kind of theft is this ? Really upset with the service !