Accounts department bad customer service

Honestly the worst accounts department I've ever dealt with. From previous reviews I can see this is not new though. My husband had been to Drs at end October 2023, payment was made by medical policy on 3 November in full, yet we have been handed over and have received threats of being blacklisted. Might I mention that from November to date I have sent multiple emails to ER Consulting and phoned to advise that payment was made on 3 November, yet they still hand me over (not a single email was responded to either) I am shocked at this lack of service from the accounts department. Now I've paid NuDebt, the debt collectors, to just stop them from blacklisting me.... Wonder how long it will take to get the refund resolved?? This is horrible service!