(1) Upon receipt of a complaint alleging an unauthorized switch in a customer's telecommunications carrier, either orally or in writing, from the customer, the customer's original pre-subscribed telecommunications carrier, the customer's local exchange company, or from the commission or its staff on behalf of a customer or applicant, the telecommunications carrier that initiated the change shall make a suitable investigation and advise the party requesting the investigation of the results. When advising the customer or party requesting the investigation of the results, the carrier that initiated the change shall provide documentation in accordance with ARM 38.5.3801 and 38.5.3802 that confirms the customer's valid authorization to switch telecommunications carriers. The burden is on the carrier that initiated the change to produce documentation that valid authorization was obtained from the customer. If a carrier fails to provide the documentation, the carrier change will be deemed invalid. A telecommunications carrier, upon receipt of a complaint from the commission or its staff alleging unauthorized switching, shall issue an initial response within five working days.