Idea Cellular Ltd. — Value added service subscription

Address:

Chennai, Tamil Nadu

I am using G.Dhanasekaran IDEA, prepaid number for my family use. In a day i get 5-6 calls from IDEA, stating value added service. Once you attend the call and close it, you are considered subscriped for the value added service.They will send a SMS, to reply immediately for unsubscriping the service. If you fail to respond, your money will be deducted for your inaction.
I have called Idea customer care about the policy of subscribing policy for value added service, they refuse to answer my quoestion and disconnected my call.

Can a service provider consider subscription, just attending their unwated calls? Do i have to send SMS immediately for unsubscriping?

They just take money from many customers without their knowlwdge? It is not CHEATING, just LOOTING ? VERY BAD IDEA.

Where as with other service providers , customer has confirm by SMS for subcription.