That's not a vac ban, that's a a game ban. check your profile, it will say game ban.
also it has a nice little INFO button next to it, click it and read it.

We don't know why you got banned, and Valve will not tell you.
we can tell you that its permanent though, and nothing you say will get it removed.

also game bans are for many reasons, so don't try the "i did not cheat" reply.

Интересно, когда люди научатся отличать игровую блокировку от вака