Who called from 2102004890

Caller ID says "Unavailable" 210-200-4890 - When I answer they hang up immediately - if I dial the number back I get a recording that says "the number you attempted is not in service, this is a recording."   What the hay is going on - that number has just dialed my phone ???????? This has occurred on my land line and cell several times.

i keep getting this number, at ist i wouldnt answer, then i did and i get the same as fedup listed above