Amount deducted without approval for caller tunes

Location/place: Bangalore

Name of company/service: TaTa Docoma Telecom Services

Hello,
3 days back , i got a call from customer care to activate the “Caller tunes”, for which i rejected . Next day , i got a message saying the Caller tunes is activated in my mobile and Rs 50/- has been deducted.My question is how come they deduct amount and activate without my approval. I want Tata docoma telecom to credit my amount.

Regards,
Shivakumar