CENTRL ISLIP - Investigators say they caught a Port Jefferson Station doctor in the act of selling prescriptions for controlled substances. Dr. Frank Telang is accused of selling prescriptions for oxycodone and other controlled substances to undercover officers. He allegedly sold the prescriptions for cash without even performing medical examinations.Officers with the Drug Enforcement Agency (DEA) raided his neurology office earlier this month. Telang allegedly kept illegal painkillers there, as well as in his car.Telang is the third doctor on Long Island to be arrested by the DEA for selling illegal prescriptions. Telang pleaded not guilty today in court in Central Islip. His attorney asked the judge if the doctor could still write prescriptions, but was told he could not.If convicted of federal charges, he faces up to 20 years in prison.