Can't pay hospital debt. What should I do?

About a month after my 18th birthday, I had my wisdom teeth taken out at the Cleveland Clinic. But, before I had my procedure done, my mother called our insurance providers at the time to make sure everything would be covered and they said yes.

About a year after that (sometime last summer), I started getting calls from a collection agency saying that I had an outstanding balance of almost $6,100 from the procedure. I told them this wasn't correct, they said it was and how could I make payment arrangements. I was unemployed at the time and full time college student so I had no way to pay and the people I spoke with told me they'd check with the Clinic to make sure everything was accurate.

A few months later, they called back and asked for a payment. I told them that I had spoken with my insurance company before I had even scheduled an appointment with the Clinic and was told everything was okay. They told me to contact my insurance company to try and file an appeal. I did. But the insurance company told me that I had waited to long to try to file an appeal and asked why I didn't contact them sooner. I had NO idea that I had an outstanding balance because I never once received a bill from the hospital or from the insurance company. By the time the collectors called me, it was well past the appeal deadline.

They called again. I asked if I should get in contact with the Cleveland Clinic to see if there was something that could be done. They (Capio Partners) told me that it was too late and that the matter should be settled with them, not the hospital. This continued for another two-ish months. "Hi, do you have money yet?"

"No. I'm unemployed but looking for work." (Which was true.)

"Is there anyone you could borrow from? Could you use your student loans?"

"Uhm, no."

"Ok. We'll call back."

Then yesterday, I got a letter in the mail (that someone accidentally threw out and I lost the ******* contact information) from a law firm about the debt going to collection proceedings or something. I had planned on calling them today, but can't since I can't remember the name of the firm to look them up.

I got a job about a month ago and was waiting on Capio Partners to call me back (they NEVER gave me the same contact information twice so I never knew who to call because they called from different locations) to try to set up some payment arrangements. I only work PRN so I can't afford to pay that entire balance but I'd pay as much of it as I can (even though I feel like I shouldn't have to).

Is there anything that can be done? Should I try to call the Cleveland Clinic even though in the letter it told me not to? I feel like it's not fair that they waited to send my bill to collection a year after I had the oral surgery done and they never told me anything about an outstanding balance. I honestly cannot afford a $6,100 bill right now AND still pay my tuition/fees for school. But I don't want to get sued or have my credit trashed at 20.