Have you tried going to the OC and seeing if they'll pull the debt back from the CA and allow you pay them. Have them request the account be deleted.
I recently had one pop up for the same amount. I wasn't present the day of service and didn't sign for treatment or payment. My spouse did. OC wouldn't pull back, wouldn't instruct to delete, and CA was an $%$ so didn't even ask for PFD. My spouse called hospital and had the account transferred out of my name, since I wasn't the one who signed.
My spouse went up and paid and has a receipt that shows the account was NOT in my name. I just mailed off the CA a nice friendly DV letter today, informing them that they have violated FDCPA, not once, but twice and urged them not to violate a 3rd time. My spouse called them after I said not to and they never did the "this is an attempt to collect a debt, any information will be used for that purpose" routine and they have never mailed me anything and especially didn't mail me nothing within 5 days of the initial communication advising me of my right to request validation or who the OC was, amount, etc.
We shall see what happens. I expect them to have the letter tomorrow or Monday.