You should fight these charges. You were not BAC tested and you were not escorted by police. Sounds like the EMT personnel were simply locating people to charge for services so your best bet is to contact your state's consumer protection agency and the board who handles such matters (regulates and certifies EMTs) and file a complaint there, as well.  Indicate that you were not so inebriated that you could not render your own decisions and you were not under arrest. Therefore, you refuse to pay for services you were not given and for something you were threatened with violence to do if you refused.