BCT auto-disable posting from ip that is previously used to spam
Only the IP originally used to register the account matters, and such accounts are disabled immediately upon being registered until a fee is paid. This is solely to prevent spammers registering many accounts with the same IP address; this forum otherwise doesn't use IP bans at all.
now what happens the person who gets banned came into free wifi zone and he started using that ip and suddenly he is banned from posting with a message that your message is marked as spam.
Nope. That doesn't happen. If a message is deleted for being spam, it is solely due to its content, not the IP address used to post it. The moderators (who are in charge of actually deleting such messages) don't even
know the poster's IP address, only the admins do, so they couldn't do that even if they wanted to.
he said he only send a 2-3 message and he never sends any message and suddenly after using that free wifi network my account get banned.
Protip: when pretending to be your "friend", keep your pronouns straight.
In any case, the free Wi-Fi has nothing to do with it; you (or your "friend") were banned because you broke the rules.
The banned account has few merits points as well.
Those merit points don't mean much now. Unless, of course, they were obtained by merit farming with your other alt accounts, in which case those efforts are now permanently wasted. Too bad. That's what happens when you break the rules.