Due to the nature of the service provided by radio-telephone utilities and the number of variables which may affect the usefulness of the service to particular subscribers, notwithstanding the provisions of section 601.1 of this Title, radio-telephone utilities, and other telephone corporations providing radio-telephone service, may provide radio-telephone service free of charge for a five-day trial period during which the subscriber may gauge the usefulness of the service to his particular circumstances. The trial service may be provided to a prospective subscriber once during any two-year period.