I donated items once and now receive an onslaught ...

I donated items once and now receive an onslaught of phone calls. I receive at least 4 calls per week, and sometimes I receive more than one per day. I have asked them to take my name off of their call list and I have emailed repeatedly requesting the same but nothing has changed. Their charity may be legitimate, but I will never donate to them again. They really need to learn how to treat their donors.