Same details as everyone else - caller said "um, hi" and the call faded out after a few seconds. On call-back I got a fax line (or a recording that made it sound like a fax line). Probably they are testing for "live" cell lines for future use in telemarketing.
Received a call "Um hi" and call went dead like it was dropped (it wasn't). Don't know what it is but I registered my cell on the donotcall (I've been receiving collection calls for someone and I've had this number for 10 years.) too weird.
I answered and sounds like guy said "uh Hi" but really there was no one there. Like someone else said, probably a robo call. Called my cell phone and that's annoying plus pretty sure it's illegal.