With every ban message there should be a moderator's name, that name is the person who banned you. If you wish to be unbanned you have to appeal, but if it was a correct ban nothing can be done.

there is no name
just sayed "banned!" 4 week duration

and the ban appeals forum page says i have insufficiant rights to post there

Strange. Have you confirmed your account by email? Also it might be because you need 25 messages.