Can I negotiate a medical bill if it falls under my deductible?

So a few months ago I called an ambulance for my partner for alcohol poisoning. The EMTs thought he was fine but he was barely conscious so I asked him to go along with them and he did. This is the first time I’ve dealt with a medical emergency so I foolishly thought since he had his family’s insurance it would be fine.

Now we owe about 3k. I think it was billed as a non-emergency, the hospital may have been out of network, and we get no help from insurance because he has a high deductible. The ambulance cost around $800 and the hospital charged $2k for, as far as we can tell, nausea medication.

I’ve read all I can find on getting itemized bills, waiving if you pay today, No Surprises, etc. but I have no clue how it applies in this situation.

Partner and family are convinced that there’s nothing to be done— they say that insurance paid the hospital, so now we owe insurance, so now we can’t contest the original bill. Is this true? Is there anything we can do?

ETA relevant info: we are 23, SC USA, he makes around 80k. this happened before he switched from his family’s insurance to his own employer insurance.

*Sorry if I used the wrong flair. I’m completely new to having insurance and am still learning the terms.