Depends on the type of complaint. If it's about your unban appeal being locked then it would be a complaint against policy. Which is something management would take care of. If it's about a staff member in particular you would have to talk to a staff lead. If it's about another player you can file a report a player if the player in question broke server rules.
If it is indeed about the unban appeal I would suggest you don't file a complaint as you already broke unban appeal rules once, complaining about the policy will just increase the chance of your appeal being denied.
Gunna be honest just be patient, the more you ask/indirectly complain the longer your app is going to take to get processed bc they will just keep delaying it or shut it down all together
You may not have broken any rules - you can prove that in your unban appeal. But what is certain is that you broke rules after you put your ban appeal in, coming onto TS asking me about it, sending 2 private messages to staff and also making a forum post about it, asking to get it dealt with. Thats 3x rulebreaks of the same rule.
No wonder why your appeal has been locked, go figure.