When someone complains, they should be able to keep track of their complaint (online would be fantastic). For that purpose, the agency should assign a case number to each complaint and furnish that to the complaining party. MARTA does this and calls the number a HEAT number.
Agencies should appoint an ombudsman who can represent the interests of riders when they submit comments, questions, or complaints. S/he would be responsible for investigating rider complaints and responding to comments.