Who called from 2136999156

This guy has called me at least 4 times a day since 9/4. I hear someone on the other end but I get no answer. Weird

This phone number has been calling me over and over for about a week. I haven't answered once, and yet it keeps calling at different times of the day. Finally installed Reverse Lookup and blocked the #.

Multiple calls. No one responds when I answer.

This number calls quite late. Who are they?

Called twice at the same time, hear someone or something on the other side, but so response.
Added the number to my reject list.