Discovery Bank refusal to cancel credit cards to continue charging fees

I called to cancel my blue prepaid credit card in 2019. April 2020 I got notifications that I owe discovery (on a prepaid credit card) where I "reminded" discovery credit card division about my request in 2019. I then cancelled the card again in April. September 2020 I was phoned by debt collectors for the very same issue I had in 2019 and again, I contacted discovery credit card to follow up on why I'm being charged interest on fees with a prepaid credit card that was meant to be cancelled in 2019. They escalated the matter to have the fees reversed and again requested the cancellation of the card. Feb 2021 and I have been charged more interest on fees for a card that was meant to be cancelled in 2019 and on fees that was meant to be reversed. Now I'm being visited by Sheriffs for fees charged on a prepaid card which cannot run into a negative, yet discovery bank makes sure that they bend the rules to suit them and to ensure that there is some sort of debt despite cancellation requests