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.
47 C.F.R. §68.415