The following practices, whether or not commonly considered promotional practices, are specifically prohibited:

1. (1) The furnishing of utility service, or the furnishing or installation of wiring, piping, appliances or equipment to any person at no cost, or at less than cost; or the furnishing of repair, modification, or maintenance of appliances, equipment, wiring, or piping to any person at no cost or at less than cost; except in accordance with the terms and conditions of service on file with an approved by the Commission and this Chapter governing the furnishing of utility service.
2. (2) The guarantee of a maximum cost of utility service to any person or for any premises or installation.