Customer complaints about bills for utility service, deposit requests or other service problems shall first be made to the utility. The utility shall allow complaints to be accepted and processed in a simple manner and form. Every utility 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 utility shall offer the complainant, upon written request, the opportunity to receive the report in writing. A utility 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. Every utility shall file with the commission its procedures for fulfilling the requirements of this section, and any changes in such procedures must be filed at least 30 days prior to implementation. A utility shall refrain from terminating, disconnecting or suspending service for nonpayment during the pendency of a complaint before the utility or the commission and for 15 days after resolution by the utility, 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, including bills for current usage, or such amounts as the commission or its authorized designee determines reasonably reflect the cost of usage to such customer.