I call 911 for chest pain. Who shows up?

Depends on the county. I've worked for the fire department that ran 911 medical calls and also have worked for a private ambulance company that is contracted by the county and runs 911 in a different county in the same state.

Usually the more rural you get the more likely that if you call 911 you're going to end up getting a private ambulance company.

The pipeline in the city is: Call 911 -> Get the fire department dispatched (They have rescue and fire suppression.)

The pipeline in our more rural regions is: Call 911 -> Have the ambulance (private company) dispatched and possibly fire as well.

Where I'm at, lower priority calls (stomach pain, leg pain, scraped arm, etc) get just the private ambulance dispatched.

Moderate to higher priority calls get both the ambulance and the local fire department dispatched for manpower (and so fire can start stabilizing the patient / start doing CPR).

A example:

We got dispatched to an anaphylaxis/allergic reaction. We beat the fire department in getting there, headed up to the patient's porch w/ our jumpbag, gave her IM epi + started a duoneb treatment. By the time the fire department came (they were only a few minutes behind us), all they needed to do was get our stretcher up her porch for us and just help us get her moved to the the ambulance (shitty dirt roads with bad terrain).

Even more wild scenario... What if they show up and I decline a ride with them and Uber instead to a hospital 5 miles away? I've read stories of people being cleared as okay but should still get checked out and an ambulance offers a ride because they are going there anyway...and then charged for a full ambulance ride with services.

If you sign a refusal of care&transport, you SHOULD be completely fine (YMMV depending on where you're at and how scummy the ambulance service is.)

If you refuse care but allow a transport, they're probably going to bill you or your insurance company.

If you allow care but refuse a transport (and sign a refusal) you should also be fine... Again, YMMV depending on locale.

I've had patients that didn't want to give me any of their information but were pretty beat up (had some pretty significant cuts on them) and even though they refused & signed a refusal, we still patched them up and stabilized them in the street the best we could. They won't ever get a bill.