ANSWER:

What they are doing is a major sin and if they deal with magic and believe these soothsayers, they have committed an act of apostasy. An apostate has no rights on us and if you exhausted all possible ways to call them back to Islam and you failed, you can cut them off.  

My grandmother & Aunt from mother side regularly visit magician & do all shirk type task as magician says. We tried to stop her from doing so by saying this is shirk or haram. but they don’t understand. there whole life they are doing this. should we cut our ties? or shouldn’t?