Complaint Review: Massachusetts Foundation Of Vietnam Veterans

This organization, called Baystate Vietnam Veterans on a website, or the Massachusetts Foundation for Vietname Veterans on caller ID, calls me every single day or night and will not stop despite numerous requests to do so.

Calls come from different locations, even Provincetown, even though the headquarters (or a least the President) seems to live in Gardner, Massachusetts. Once when I told the caller that they had already called that same day, they denied it, using the usual "I never called", a legalism supposedly covering the fact that someone else from the organization/office did call.
This is maddening. What can I do?

Margo
Melrose, Massachusetts
U.S.A.