Airtel — deduction of money from my airtel account for an unsubscribed service.

Address:

Chandigarh, Punjab, 160036

I just received a message stating that due to some "Bhakti sagar potrait" service, Rs. 20 have been deducted from my Airtel account.
I never opted for the mentioned service and no kind of approval was asked from my side.This is really bad on Bharti Airtel's part as they are just flushing people's money without any appropriate reasons.
This kind of service was not expected at all.