Here are some tips on how to deal with Spam.
1. Ask them to please stop.
2. Add them to an your ignore list which is next to the friends list icon. Note you need to readd their name each time you relog.
3. Contact any staff members if they are on and free to help you.
NOTE: Adding them to your ignore list is the best way to go, because sometimes a staff member can't mute them and going off on them will only make it worse for the most part...