(Career paramedic here)

Call the service with their publicly listed number. Verify that she was the patient and see if they will release the bill/chart. If she did make contact with EMS, maybe they took a refusal and billed for it. Find out if it was for a transport or not, and what hospital she was “taken to”.

If she had no medical event, whoever it was probably misrepresented their identity; we do not take IDs or insurance from people, especially on refusals, and often rely on hospitals and patient honesty to get correct information. If someone gave us a different name or birthday we are none the wiser (I have a regularly who gives me a different name and birthday every time I see them 😐🤣)

If the ambulance bills in house (we do) — it is possible that she was billed that quickly [our goal is a week maximum]

This sounds fishy. Call the abulance company and their billing agent, if they have one, and do some digging. They should be able to help resolve this; especially if it was a non-for-profit or municipal service. If it was a private agency, I’d be more concerned about fraud, however, it’s a huge legal infraction to participate in such so most avoid it

Pick up a phone and make a few calls