Fraudulent credit card transactions

Last night I got 4 sms of transactions that I did not initiate. No OTPs received. I immediately called the bank and they blocked my card. They said they have to wait for the merchant to accept the fund on the transaction and then the bank will request the merchant to reverse it and do investigation.

Anyone had any experience on this? How long did the bank take in reversing the transaction? Should I pay the fraud amount?