Why would you not take the advice of WC? They were giving you good advice. They were right, you had no choice but to use worker's comp for an on the job injury, that's the way it is supposed to work. You are NOT allowed to use your own insurance and pay for it out of your pocket, even if you are dumb enough to want to. So let's see. Both the hospital and the doctor's office used the wrong coding?
If the hospital and the doctor can't figure out how to code this bill, and keep calling you, don't talk to them. This is between them and the worker's comp division. That's all you need to tell them, and then then hang up. If they (one or both of them)have turned it over to an unscrupulous collection agency, even more so. They may tell you they're coming to your house tomorrow to take you to jail or something, but they're just hoping you will be dumb enough to send them the money, or part of the money. Keep referring them to worker's comp. It's not your problem that they won't talk to worker's comp. Worker's comp does not have to talk to them. They've found you an easy victim who keeps talking to them, and they've got you scared, and they're pursuing it.
They may threaten to damage your credit, they may threaten to garnish your wages, but really, have they done this yet?