They call a couple of times a day. If I don't know who the caller is that is on the caller ID, I let the machine answer and they don't leave a message. Just sit there for a second then hang up. When I called back there was silence. But one time I answered and put a phone blower in the phone. But they keep on calling.

I work with students in Africa & do not answer phone calls from numbers that have a country code or look like they are coming from outside the US (otherwise I would have phone calls coming all day & night from students seeking sponsorships).  Anyway, I took a call from 971-231-1202 thinking it was someone here in Portland, and it turned out to be a student in Africa... who was calling from Africa... How do they get their number to ring through a US (and local!) phone number??