BSNL — Unsubscribe VAS from my number

Address:

Murshidabad, West Bengal

Sir,
A VAS service called Joke service is activated on my number from 55888. And it is renewed every 7 days and Rs. 15 is deducted although I haven't activated any services. When I call the customer care he asks me for an installation ID but there is no installation written in the sms. The sms is as follows:- "Rs. 15 charged. Thanks for using our Joke Service. Your service has been renewed".
Kindly deactivate all the services activated on my number.
My number is [protected]