Customer complaints about bills for telephone service deposit requests or other service problems shall first be made to the telephone corporation. The telephone corporation shall allow complaints to be accepted and processed in a simple manner and form. Every telephone corporation shall promptly investigate any complaint in a fair manner and report the results to the complainant. If the report of the investigation is made orally, the telephone corporation shall provide the complainant, upon request, the report in writing. If the complainant requests the report in writing, the telephone corporation shall send such report in writing within five business days after the request by the complainant. In the event the corporation is unable to give an oral report due to the unavailability of the complainant, either a letter requesting the customer to call the telephone corporation or a written copy of the report shall be sent to the complainant no later than two business days after the results of the investigation are determined. If a letter requesting the customer to call is not responded to by the customer in five business days, a written copy of the report shall be sent to the complainant no later than the seventh business day after such letter was sent to the customer. A telephone corporation resolving a complaint in whole or in part in its favor shall inform the complainant of the availability of the commission's complaint-handling procedures, including the commission's address and telephone number. A telephone corporation shall refrain from suspending or terminating service for nonpayment during the pendency of a complaint before the telephone corporation or the commission and for 15 days after resolution by the telephone corporation, or by the commission or its authorized designee, unless otherwise provided by the commission or its authorized designee; provided, however, that as a condition of continued service during the pendency of such dispute, a customer shall pay the undisputed portions of any bill for service.