Started today every 30 minutes. Found the source:
Hawaiian Unions Photography
121 Hale Kapa'a Court, Pa'ia, HI, 96745, USA
Phone: 1 808 555-1212
Toll Free: 1 800 555-1214
Fax: 1 808 555-1213

It says it is gay and lesbian photographers. Probably someone with a life trying to disturb others radomly.

This number tried calling me every few hours, even in the middle of the night. Silence on the other line. Very annoying!
Caller ID says Dir. Assistance.

Got a call from a 808 555-1214. Said "Hello" several times, no answer.  Location stated UnitedStates.  Seems like the same situation like the 808 555-1213(?). I put a block on this number after reading all the above!