Maryland Code, Public Utilities § 8-401

(1) the telephone company or reseller selected by a customer until the customer provides express authorization for a change to another telephone company or reseller;

(2) for telecommunications service options for which the telephone company or reseller imposes a charge, the telecommunications service options selected by a customer until the customer provides express authorization for a change of telecommunications service options; or

(3) the person who bills the customer or the customer's billing arrangement until the customer provides express authorization for a change of the person who bills the customer or the customer's billing arrangement.

(1) provides telecommunications services to end-use customers by using the transmission facilities of another person, including wire, cable, optical fiber, or satellite or terrestrial radio signals, regardless of whether the reseller possesses its own switching facilities; or

(2) bills an end-use customer or causes the customer to be billed for telecommunications service.