If someone’s bothering you on Facebook, the best way to stop them is to block them. Learn more about blocking. Other ways to limit someone’s ability to contact you include:
- Unfriending them: Only your friends can post on your timeline. You can also change your settings to prevent anyone from posting on your timeline.
- Blocking their messages: When you block messages from someone, they’ll no longer be able to contact you (ex: send you messages, call you) in Messenger or in Facebook chat.
Source: https://www.facebook.com/help/131898986885140?helpref=uf_permalink