Pathcare error with submission

In Sept 2019 I had my oncology blood tests done. The bill got submitted and rejected by Discovery. Pathcare Rejection Dept does not investigate WHY the bill was rejected. 6 months later, in 2020, they send me the bill to pay which I then query. I then establish from a lady in their Rejection Dept that a wrong Doctors code had been input by Pathcare so they then tried to put it through again to Discovery. Discovery declined to pay it because it was now outdated as it was now 2020. I cannot find one person to resolve this matter. My oncology is covered 100% by Discovery and all this could have been avoided if the first person who got the Rejection actually checked to see that the code was wrong. Now a lady in Feb 2021 phones me to pay this bill which I refuse to do. The person who made the mistake must be held accountable for the error and Pathcare can take the loss for this bill. Absolutely *********** staff and all you get told is it will be referred up the line but no one comes back to you. I have all the emails and names of who I queried this with and all of this could have been avoided if the first person took responsibility for finding out what the problem was.