Claim not paid after numerous promises to do so

Somewhere around the first or second quarter of this year I followed up on a claim which was never paid for an in hospital procedure. I was surprised that they didn't claim as I had been given pre-authorization for the procedure and confirmed that the procedure is paid for by them if in hospital which they confirmed. When I queried why they didn't pay, they seemed slightly confused themselves, then said that the procedure isn't covered under my plan which would be fair enough if they didn't originally tell me that it would be covered. I asked them to lsiten to the recordings of my initial conversation and they agreed that it should be paid because that's what they told me. I will not go into the detail of it but without exaggerating, I have spoken to about 10 different consultants, each promising me that they would take care of it. I managed to get two of them to actually provide me with some feedback and one confirming that the payment to the doctor is being made, I don't need to worry any further about it. So obviously I was unpleasantly surprised when around 4 or 5 months later I receive bill from the doctor which is was still unpaid. I have since had to pay it myself.