If a member of a cult is harassing you, try sending this Cease and Desist Letter/Order to them and the local police to establish a paper trail. This one has been used extensively against the Opus Dei cult:
This CEASE AND DESIST ORDER is to inform you that your and the Opus Dei cult's harassing and intimidating actions against my fellow Catholics and I has become unbearable. Such anti-social behavior is completely unacceptable and will not be tolerated in any way, shape or form. This letter is to demand that your and the Opus Dei cult's continuing involvement in, planning and encouragement of, high-pressure recruitment, information gathering, harassment and intimidation must CEASE AND DESIST immediately. Should you and the Opus Dei cult continue to pursue these activities in violation of this CEASE AND DESIST ORDER, we will not hesitate to pursue further legal action against you and the Opus Dei cult, including, but not limited to, civil action and/or criminal complaints.