No security with online transactions

Very disappointed by Discovery Bank. On the 10th of November I received a notification of a transaction in dollars. I immediately notified Discovery of the ********** transaction and they canceled my card. However they do not want to reverse the transaction as the vendor has provided "compelling evidence " that I authorized the transaction. Their so-called compelling evidence includes the name and email address of a total stranger living in the US. I would love to know how they got their hands on my card details and also how the OTP system was bypassed. I always have to provide an OTP with online transactions and for the ********** transaction one was never received. I no longer feel safe banking with Discovery and will be canceling my account. I would advise people twice when shopping online with a Discovery card. I have had a Discovery card for years and while FNB managed it there were no issues whatsoever