Chat and Ranked ban...

Finished my ranked, won most of the games and a day after I receive a chat and ranked ban, for absolutely no reason at all, they didn't tell me why i got it just that i am banned. The only report i got was for spamming veigar joke and taunt in an ARAM, didn't flame just spammed. Surely they cannot ban you for that? The system is either way too harsh on a little thing like this or doesn't even check chat logs and just insta bans you