paid up account but harrassed

I called in requesting a balance on my accounts, on the 8th Feb I received an email qouting me the settlement amount and the discounts applied, valid until 28 Feb 2023. I made payment on the 18th Feb 2023 as per email. In the week that followed I was hounded by Capital data MBD and Newtons Attorney agents calling me demanding payment. I have informed them that I did make payment and provded proof of payment. In the weeks that followed and to date I am still receiving calls demanding payment. I spoke to Nazeera, whom I explained the story to again last week and she asked me to send an email to Samantha, apparently Samantha deals with these sort of queries. Samantha has still not contacted me yet I am getting calls still demanding payment. I am not sure what is happening at the company but I have one more account that is still with them and would like to settle it but I am not getting any hope as they refuse to give me a proof of account closure letter and insist I still pay more money than I was emailed to pay. Please assist, I am annoyed and frustrated