Am I obligated by law to pay an unreasonable amount for emergency medical transport?

Jeeeez. Please don't assume what you get on any internet site from anyone (including me) is 100% correct. Get a competent lawyer who represent your legal interests and that you trust. Then if she messes up... at least, you can sue her for malpractice. If you are on a direct contract with the insurance company (your own policy) or an employer provided policy (that is prior to the very good reforms put in with the Affordable Care Act in 2014 which helped you even more) AND the transport provider was under a contract with that same insurance company (also called in "In Network" or on their PPO provider lists) THEN your only possible (and I mean possible) obligation is the percentage of the co-pay provided in your insurance contract. Some insurance contracts with their provider require some additional amounts to be completely WAIVED and not billed to the insured. Also, if you are receiving ANY FEDERAL benefits for medical service, you also can not be legally billed for the additional amount as well. OFTEN, since Texas has such poor laws and government with the fanatics now in control, medical providers will that they are owed the balance of the unpaid amount such as I believe you are being subjected to. It is a potential violation of Texas Insurance law (even still) and Debt Collection laws. Please keep all your evidence and only communicate with them all in writing or emails. THEN, go see a consumer oriented plaintiff's lawyer. We don't have any "agenda" to impose our views on folks who suffer injury or damages and believe that the Law is also there for people.... so are businesses. Best wishes, Edward