Who called from 7866647971

I got one call and then one hr later another. when I trIed to text it  no responce then I tried to call it bk and a recording says ur call did not go though. So I tried to call it from my boyfriends phone and same thing call did not go trough and they never left a message on my voice mail. Is there any way to block this and any other unknown caller and 800 numbers? Any help would be appreciated thank you kindly.

THIS NUMBER KEEPS COMING UP ON MY CALLER I D BUT THEY NEVER LEAVE A MESSAGE.
WHEN I TRY CALLING BACK , I CAN'T COMPLETE MY CALL.

THIS NUMBER KEEPS COMING UP ON MY CALLER I D BUT THEY NEVER LEAVE A MESSAGE.
WHEN I TRY CALLING BACK , NO ONE ANSWERS

This number called Me twice so far today, about 3 hours apart.  I don't pick up calls I don't recognize and they don't leave a voicemail either........so, frig em !!  =)

I have received 2 calls from this number to my cell phone and no answer when it comes through.