@vivek
1) tell your parents. They'd know soon about it anyway and this situation will not be resolved in a short time, if at all, in your favor.
2) SMS you got clearly says do not share with anyone. Yet you did. You are then liable for the transaction that subsequently happened.
3) did you record the call asking for your OTP and your giving it ? That and all other recordings could help you.save the original recordings, SIM card and Mobile. Take backups.
4) as already said, you will have to lodge a police complaint making sure you get your facts right. Your claim,if at all, will lie against the person who used your OTP, based upon evidence you provide to Police and their further investigations.
5) The Credit Card issuer will collect amounts from you. Delaying this will not help you IMHO.
7) you should ask the website proof of what actually has been purchased and the address it has been delivered to. You / Police will need it.