I'm sorry people are treating you that way

If they don't want to give you the chance to defend yourself, then that reflects the kind of people they are. You don't want to be friends with someone who assumes the worst of people anyway. So if they want to block you, it's their loss. They've lost a good friend due to their own ignorance. And a true friend would never do that to you.

I don't think you should self harm, though. Some people just feed off drama and like to hurt others when given an excuse (which I'm sure you found out today). So please don't hurt yourself too. It's not worth it. They want you to feel hurt and insulted, which is not something a true friend does.

Of course that doesn't make it any less hurtful; I've been in these situations myself also, so I know what you mean. But don't give them what they want or hurt yourself.