Mr. Chairman, exchanges regarding the grievance process are made in writing. This is an arbitration process, if you will, in the context of which exchanges are made in writing. The board has the power to hold hearings and to ask people to appear before it. Apart from that, submissions are made in writing.
As for the initial authority, it is hard to say what rank that person will have. It has to be at least the individual's commander or supervisor or the person who can deal with the issue. It can't necessarily be concluded that it's always the commander. It may be him, but it may also be a person who is able to provide a solution to the complaint.