Outstanding letter of account closure

I closed my Edgars account in June 2021 with a R0 balance. I was promised a paid-up and closed letter within 48 hours. Now I am being harassed by a debt collecting company for an outstanding balance??!! I no longer want to try and sort this out with Edgars/RCS. No answer from any phone numbers or emails being answered. I am sick and tired of not being assisted to. All I am asking is a letter that my account is closed with a NIL balance.

I have all my email trails of communication - including the email from Edgars Closure confirming my account closed and the promise of an official letter within 48 HRS.

I want the official company letter send to me that my account is closed and the credit beareau's to be notified accordingly.