آپ can block MESSAGES from them and آپ can prevent them from posting on your دیوار if آپ aren't a پرستار of them. I don't think آپ can block them from seeing آپ though. But,if he is stalking آپ یا bothering آپ then آپ should tell one of the admins to get him banned/suspended یا even IP banned where he CAN'T make another account on the device he is using. (Unless he gets another one and goes through that.)