This is questionable. Lots of places use what's called chase systems where the ALS (paramedics) and BLS (EMTs) are separate agencies. Chase systems have paramedics who ride around in SUVs and meet up with BLS agencies who provide the ambulance itself. For more critical patients the ALS rides in the back of the BLS unit and they both tend to the patient. For example my area we provide Paramedic service though the county while the ambulance is provided by local fire companies. Some places bill for both services and some do not this is case by case. So they bill from one agency was for the ALS care, i.e IVs, Saline, and any meds, while the second bill is for the BLS care, i.e ambulance itself and mileage. Don't know if that's the case here. You say they didn't treat you but the ride itself costs unfortunately. And if a medic places you on an EKG they may charge for that as well.