FNB VIRTUAL CARD - IS TO SAFE?

FNB Virtual Card - In December 2022 I used my FNB virtual card to make a payment to webmail. I used my virtual card as I knew that the CVV number changes every hour, so therefore I was safe in the fact that they would not be able to debit my account. Surprise - on the 06.06.2023 I received a message from FNB that my virtual card was debited with an amount of R474. I immediately contacted FNB and was told to cancel my card and I had to lodge a complain with the ***** department - I followed the instructions. I had to fill out a dispute form and email it to debit card disputes department. I had done all of this while the transaction was reflecting as pending on my cheque account. FNB allowed the transaction to be processed and to add to that on the 09.06 they allowed another transaction from webmail to be debited to my account - card had been cancelled on the 09.06.2023. It takes anything from 7 to 30 days for FNB to investigate. I received an email from Bianca (no surname provided on the email) from the dispute debit card division stating to me that webmail is a subscription service and I would need to contact them for a refund and that since it is subscription service they (webmail) dont need the CVV number in order to debit my account. Why then does FNB have a virtual card with changing CVV number every hour - and more importantly where do they state that if it is a subscription service they have no authority but to allow the transaction to be processed. The reason I used the virtual card is because to me, with the CVV number - then my card cannot be debited!