1. keep everything in writing.
2. ask who hired him. I think you only hire the major doctor. and this doctor rent hospital and hire other assistant. So you have no obligation to pay him.
3. Write the collection company to provide you all the evidence in writing that you own the doctor money. By low, the collection must provide you all infomation in 30 days.
4. If you get the infomation in 30 days, you may find whos mistake and just tell them that was not your fault to mis the claim time. If they do not provide you info in 30 days.The case is dismissed.