Failed to porvide Paid in Full Letter 2 years ago

MBD debited my account throughout 2021, I then contacted them and asked for a final amount so I could pay the final balance. They said that the debit order was already scheduled for the month and I should contact them after it has gone off. I did, and I arranged that they debit my account for the final outstanding amount. I then called them a week later, asking for the paid in full letter - it is now 2 years later, and they have failed to provide this letter, and have proceeded to sell their debt to another debt collector named Nimble Group. I now have Nimble Group trying to collect an amount for an account that I closed 2 years, ago, and they've marked me as a late payer. I have tried contacting Nimble Group, MBD, and TransUnion to no avail. They are all too happy to collect money, but fail at basic administrative duties like providing a paid in full letter. When trying to call their offices, the phone says you're in line to hold, when you eventually become caller number 1, it says they're experiencing high call volumes and can't take the call - convenient.