Doctor office collects x amount for treatment/copay at time of visit. Insurance covers x amount after treatment filed. Patients are now due a refund of x amount. Months later, patient returns for follow-up-no copay collected, just subtracted from amount of refund and patients not given details regarding money owed to them. What is the amount of time required for doctors office/billing to issue a refund to patients? Are they required to notify patients of credit on account at ime of visit?