47 C.F.R. § 68.415
Hearing aid-compatibility and volume control informal complaints
Persons with complaints under §§ 68.4 and 68.112 that are not addressed by the states pursuant to § 68.414, and all other complaints regarding rules in this part pertaining to hearing aid compatibility and volume control, may bring informal complaints as described in § 68.416 through § 68.420. All responsible parties of terminal equipment are subject to the informal complaint provisions specified in this section.