Medical Billing Dispute: contractor left job incomplete

Using a throwaway bc my boss knows my main. Ok so i'm dealing with a situation and need some guidance.

contractor left job incomplete. I've been dealing with this for about 2 months now and the situation isn't improving.

I have already tried to resolve this directly but got conflicting advice.

What's the typical outcome in situations like this?

Real talk: i've dealt with this before.

In my case, it took about 1-3 months to resolve. The key was escalating to a supervisor/manager haha.