47 C.F.R. § 68.415
Hearing aid-compatibility and volume control informal complaints
Persons with complaints under § 68.4 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.