Any group accident and health policy may provide that subject to any written direction of the insured in the application or otherwise, all or any portion of any indemnities provided by any such policy on account of hospital, nursing, medical or surgical services may, at the insurer's option, and unless the insured requests otherwise not later than the time of filing proofs of such loss, be paid directly to the hospital or person rendering such services; but the policy may not require that the service be rendered by a particular hospital or person. Payments so made shall discharge the insurer's obligation with respect to the amount of insurance so paid.