You can pay the claim, you can try to reason with the chiropractor for a reduction of the bill, or you can decline to pay and see if you are sued or if it is referred to a collection agency. If you are sued, you can assert whatever deal you had and any billing irregularities as a defense against the debt. If it is reported to a collection agency you can dispute the debt, although I expect that the chiropractor's office would simply affirm that the amount they reported is accurate. You can also consider a lawsuit of your own to resolve the debt, although procedurally it's usually easier to bring a counterclaim if in fact money is owed. If you believe worker's compensation was billed for services provided to your wife, it can be assumed that they will be happy to investigate.