Online Shopping on my Account

I'm so dissapointed in this Bank, on the 24th December at 17:07, there was an online purchase that was done on my account without my permission, with the amount of R325. 25, again on the 28th December at 17: 17:13, there was another purchase with the amount of R627. 58, also without my permission, on the 29th December, I went to the bank branch to report this 2 purchases, and the guy who helped me that day, told me that those transactions are online purchase, and there's no way they can reverse the transaction if it's done online, I asked him if my money is not safe in their hands, and he said, unfortunately there's nothing that they can do, all I can do is to cancel the card and do the new one, and I did that, I logged a complaint to Obssa, and Obssa told me that they'll get back to me if that problem is not solved within 10 working days, on the 10th January 2023, I got my money back into my account, thanks to Obssa, yesterday again, there was a purchase of R627, 58, with the same people,

Can Hello Peter help me solve this problem please, because according to my knowledge, there's no transaction that is going to be through without authorization code from the bank, how did this get it right to go through my account, doing online purchase without authorization code (OTP)