One excuse after the next

I have a claim dating back to 2015. Before I had my transplant bloods were done and should have been paid from the transplant auth benefit. Bankmed had copies of letters auth and motivation for everything. They rejected the claim the. I had to send an email asking them to put it through. Had to follow up a week or two later and there was still no response so obviously I figured they had sorted it out. Now the pathologist sends me an account for that claim stating Bankmed hasn't settled. I enquire and they tell me about anything g over 4 months becomes stale and for them to 'consider' ,asking payment I must send proof of my 1st enquire which I did. Now they saying it won't be paid because I need motivation letters fro. My specialist requesting for those tests to be done. Why if everything was sent months ago do I need to repeat this. And the. Get told they will 'consider'. I'm tired of their call centre I. Tired of emailing I want so one assigned to this case to get it sorted out with high priority. I don't see why their slip up has now become my problem to sort out and look for documents which they have on file.