My question involves malpractice in the state of: Georgia

My son has Chrohns and he has remicade for treatment. Last year he switched insurance and during that time 1 treatment was paid by his insurance , but a year later they took the funds away from the doctors office because it wasnt covered. Since then his new insurance has been effective and paid all claims. As a result of this isssue the doctor wont treat him, even though the current insurance is paying correctly. Is there anything he can do legally? He is on disability and cannot afford to pay what they say is a $14,000 balance. They havent asked him if he could afford a monthy payment or any negotiation, they simply wont treat him. Does anyone have a suggestion?

Thank you,