Labcorp Changing CPT codes Burlington North Carolina

I had to get a test that was outside my insurance network.  I was given a CPT code by the physician and the facility that was being used to get authorization for my insurance to pay for the coverage of the test.  Paperwork has CPT code on it that was given by the physician.  I then get a bill from Labcorp.  They decided to change the CPT code.  My guess is that they were trying to up-charge the test.  They refuse to change it back to the CPT code that is written on all of the paperwork and precription for the test.  I spoke to several supervisors who each time just got more nasty and would never answer my questions even if it was just yes or no.  They changed a CPT code based on what they wanted to change it to, not based on the order from the doctor.  My insurance company of course won't pay for it because it's a different CPT code and I can't send another authorization request so now I am stuck with the bill.  I would have never gotten it done if I would have known I would have ended up having to pay out of pocket.  LabCorp is shady and commiting fraud.