Debt collection

I don’t remember my account number with WD, but I had 6 months of dental work, topping off with a new bridge ending in March of ‘21. In August of ‘22 I get a debt collection letter saying I owe $1000. From what?? I inquired. WD claims that my insurance never paid their share for the work done. I contacted the debt collector, and an investigation took place. Found that WD was in the wrong, and the collections were cancelled against me. WD was not happy about this & reopened another collection thru a different collection agency.