Amazon India — unauthorised transaction

Website:

www.amazon.com

I am a member of Amazon.in and recently an unauthorised transaction from my credit card has been done in the name of Amazon prime membership which I have not opted for. The transaction has been an international one through Amazon.com o[censored]SD99 and both the ends are not helping to resolve .!
I am continuously mailing Amazon.in but they are not replying saying the deduction is through Amazon.com same issue is with Amazon.com, they are not resolving saying I am a member of Amazon.in not .com
It's my credit card payment which is of crucial importance !
I have neither opted for prime membership before nor recently renewed it