First of all report it everytime with ingame tickets if anything comes towards you ingame, they will have to react to it, it is important that you do not stir it up more yourself due to then they see it two ways and let it fade out.

Report everything the person do towards you, eventually they are forced to do something about it, if the person get a warning... then next time if keeping on going it would be a few days off and then the punishmenst stack up to the 10 day suspension period... from there on it is either account termination or an extreme stern warning at the point of no return if doing anything again.