(a) Except to the extent otherwise ordered by the commission in accordance with this subchapter, the holder of a certificate of convenience and necessity may not discontinue, reduce, or impair service to any part of the holder's certificated service area except for:
(1) nonpayment of charges;
(2) nonuse; or
(3) another similar reason that occurs in the usual course of business.
(b) A discontinuance, reduction, or impairment of service must be in compliance with and is subject to any condition or restriction the commission prescribes.