In general, seeing "UNBOUND", followed by a series of numbers on your Caller ID, should be proof the call is (at best) spam, or at worst, a scam.
My first guess is that the numbers identify the spammer/client, and "UNBOUND" identifies the calling or "marketing" service.
Other
5
May 3, 2014
This number called yesterday (May2, 2014) and again today. CID indicated "Unbound 15182" which I have no idea what it is. I did not answer either calls and of course no message was left on the answering machine. Could possibly be FOP, or it could be another scam. Either way, not going to be answering the phone.