Cyber bullying causes little to no harm. Yes, sending rude messages online isn't a nice thing to do. And yes, it's ok to be a little offended if this happens to you. However, comparing cyber bullying to real bullying is, to be quite honest, pathetic. Click the damn block button. It's not hard.
You are clearly a moronic moron who deserves what is happening to you. No, don't get an adult, it won't help. Cyberbullying is perfectly okay, and you are a fool if you don't accept that. Scratch that, you're a fool anyway for daring to question it. Now think about what you've done. Also, YOU SUCK! YOU SUCK! YOU SUCK! Also, I know everything about you, and nobody likes you. So you suck, and nobody likes you, because you're a worthless thing barely worth the effort of insulting, to the point where me using profanity would validate you.
-Some idiot attempting to get a rise out of you.
Now, on to the serious bit. Cyberbullying is very easy to avoid. It's called "screenshot and block". Just telling them you're recording the conversation for possible forwarding to the mods, and referring to a "no-cyberbullying"policy will stop the average cyberbully. If it's a sock-puppet, rest easy in that idiot's cowardice. It's as simple as that.
I'll grant it can be serious depending on what it is. If someone is posting embarrassing photos of you online they took without your consent, or if they are spreading malicious gossip then that's really serious. But those things are already covered by laws and you can pursue legal action for libel, invasion of privacy, and defamation of character. But if someone is just being rude, block them or report them to the moderator.