Doctor miscoded my yearly checkup blood tests and now won’t return my calls

I went in for my yearly checkup in May and had a normal visit overall with no specific subjects discussed that would turn the visit into a specialist visit under my Highmark Platinum 750 plan which supposedly covers routine checkups with only a $10 copay. Fast forward a couple weeks I receive a bill from Quest Diagnostics for ~$600 for the blood work and upon checking with the benefit advocate center my work provides they inform me the doctor submitted my bloodwork with the wrong code so it didn’t count as my yearly bloodwork exam. They also tell me that in order to fix the issue I’d have to get the PCP’s office to resubmit the claim with the correct code. I started calling the PCP every day for a couple of weeks with them saying they would call me back or have billing get in touch with me but they never do. Now they aren’t returning the calls at all and my Quest bill is almost 2 months overdue and I don’t know what to do to fix this. Any help or guidance is very much appreciated, I can’t seem to get any traction on any side.