It may depend on what you can prove and what your jurisdiction is.
If you were in New Zealand (we have reasonably strong consumer protection laws), and you could prove (on the balance of probability) that your doctor said there would be no cost - then he would be liable.
Another question would be "Who billed you, and who did you contract to". If, for example, you contracted to the doctor, and all communications were between you and the doctor, but you got a bill from a third party (ie testing company), then they would have to prove you had a contract with them - which you probably didn't.
I'm not sure you don't have "legal recourse". You would not typically take a claim (although in some jurisdictions you can), but you should put your dispute in writing. If the other party don't accept it, they would make a claim and you would defend it (Its probably cheaper and easier that way, and fits better with the way the law is structured). THE IMPORTANT THING IS TO DISPUTE THE CHARGES - otherwise you may be seen as accepting them.
Consequences of refusing to pay could be a bad credit record, depending on how you handle the matter, and/or possibly some time in a courtroom/tribunal with additional fees. They may or may not be able to refuse you service in the future (normally they could, but it may be different with the medical practice)