(a) Whenever the employee has made his initial, free choice of an attending physician, he may not thereafter change physicians without the prior written consent of the employer (or carrier) or the district director. Such consent shall be given in cases where an employee's initial choice was not of a specialist whose services are necessary for, and appropriate to, the proper care and treatment of the compensable injury or disease. In all other cases, consent may be given upon a showing of good cause for change.

(b) The district director for the appropriate compensation district may order a change of physicians or hospitals when such a change is found to be necessary or desirable or where the fees charged exceed those prevailing within the community for the same or similar services or exceed the provider's customary charges.