Help—$8k bill

I have a complicated question. When I was 28 my digestive issues got so bad that in 2019 my former gastroenterologist performed a colonoscopy and endoscopy. They found pre-cancerous polyps and told me to come back in a year or two to get a follow-up colonoscopy because two family members have died of colon cancer.

Fast forward to 2022, I moved from MA to RI and had a new insurance and a new gastroenterologist. I told my doctor my insurance wouldn’t cover it unless they had a prior authorization bc Im under 45. I sent over my medical records from my previous gastro. The doctor’s office said they got the prior authorization and that it was covered. I don’t have proof of this other than verbally, but I know I wouldn’t have gotten it if I didn’t get a prior auth because I’m absolutely broke after grad school and v cautious about money (to a fault).

Cool great, colonoscopy happens—twice— once in May and once in July bc first one failed. Never paid anything other than $100 for pre consultation.

I just got three bills in the mail for these two procedures, and it’s the first time I got them. They total about $8k.

I called my insurance and they said that they didn’t have a prior authorization on file. Which means my doctor either lied to me or the form just got lost somehow. what do I do about this? I know I can appeal it somehow, but how do I do that? And would it be best to ask the current doctor and the former doctor to send over my medical records and advocate for me? However, I think the main issue was at the doctor didn’t actually do what they said they were going to do and then told me it was covered but I have no proof of that.

Please help, I’m in so much cc debt bc i couldn’t afford to pay my taxes last year and I don’t have a job right now, Ive been searching for months and my student loans also kick in soon.