I'm afraid posting here won't help you or get you unbanned. Try finding the servers website, usually they could have ban appeal forums. Other then that, i'd say theres a high chance you won't be unbanned. You surely must of done something wrong. Sorry to hear it.
The excat same thing happened to me only me and this other guy i might on minecraft (BomBax3)were working together on building a tunnel underground and this guy who just joined(Sirnopants) banned like three other people and then he banned me for no reason only I was on the server ANIME pixel art [MCLawl] antigri