No telephone utility shall abandon all or any portion of its service to the public, except for ordinary discontinuance of service for nonpayment of a lawful charge or for violation of rules and regulations approved by the commission, unless written application is first made to the commission for the issuance of a certificate authorizing such abandonment, nor until the commission in its discretion issues such certificate. Any application must also be served on the Office of Regulatory Staff at the same time it is filed with the commission.