This question isn't about appeals or writs, but I'll answer it anyway.
Ambulances and other emergency services often serve people who are not in a position to negotiate a contract or to decide whether to accept or reject the service. That does not mean the beneficiary can refuse to pay the bill. If the services reasonably appeared necessary at the time, then the provider can recover their fair value.
If patients like you could get out of paying your bills because you didn't consent to the service at the time, then there would be no incentive for ambulances, hospitals, doctors, etc. to treat the people who most desperately need their services. As a result, these services would become scarce -- or even unavailable -- to people who are not fully conscious and in control of their faculties.
Perhaps you can dispute the amount of the bill or argue that you shouldn't have been transported by ambulance at all, but the argument that you didn't consent at the time is unlikely to get you anywhere.
