You are probably pissed off. Emotions will not help you out though, so better do not spend time into emotions but prepare for a battle.

The first thing to do is to check carefully if the bill that s not paid is for treatment covered under your policy. It might happen that you have used a treatment that is not covered anyway. If this is the case you have nothing to do but to pay the bill. If, however it should have been paid by the insurers you should make a claim and seek your rights.

Gather all of your health insurance documents. You should have the contact, the policy documents describing what your insurance covers, all of your doctors and hospital bills as well as all of the correspondence you have with your insurer.

The next thing to do is to contact your health insurance company. You can call them or arrange a meeting. Explain what your problem is and ask them to look into the bill once again. If your policy states this kind of bill should be paid they should not argue with you. Be specific when you talk to the insurers. Tell them which part of the policy states this bill should be covered.

In the unlucky event that your insurer denies paying the bill even after your complaints, contact the state's department of insurance. They should be able to investigate your case further and reach a satisfactory outcome.

Of course you can do things in slightly different way. An insurer may deny paying when you ask them to do so, but if your lawyer contacts them they might be nicer and agree to pay. Keep in mind that hiring a lawyer may be expensive so think carefully if you want to do this or not.

The worst thing that can happen is that if your health insurance company refuses to pay a large bill and then disappears. What this means is that you have become a scam victim. You can report the scam however you should start making arrangements for a new health policy and still deal with the unpaid bill. Be careful to guard your credit by paying on those unpaid bills.