Sad but true. Oxycontin is (i believe) a class III drug, which means the prescription is in triplicate form and a refill cannot be called in. You have to get another prescription from your doctor each time.
Oxycontin is Schedule II, which is even more restricted than Schedule III. I think the triplicate prescription thing depends on what state you live in, but there's no question that the DEA has gone very Big Brother on doctors, to the point where many absolutely will not prescribe many drugs that have even the slightest chance of abuse (such as Xanax, Valium, etc, that are only Schedule IV), because they're TERRIFIED of the DEA; they allow the patient to suffer to cover their own butts.
The situation has gotten so bad that a few years ago the FDA had to institute a whole new set of regulations that COMPELS hospitals to treat patients with as much pain medication as they need; the hospitals can lose their accreditation if a patient is allowed to suffer because of a scared (or old-fashioned "deal with it" *sshole-type) doctor.