Hi
,
your best action to take when being harassed by a user in private messages is to directly block the user as mentioned in post #3, if you're being followed and spammed by the said user you may also report the post using the report function and members of staff will deal with it accordingly, it is best not to engage or confront him/her as two wrongs don't make a right.
Do send me a PM if you have any addition questions in-regards.
Peace!