Who called from 5612867765

I DO NOT RECOGNIZE THIS NUMBER

I just got a call from this number and while I was saying Hello, my other line rang again with the SAME number.
When I attempt to return the call from my cell phone it has a BUSY TONE yet when I try calling from Hospital (my place of employment) an operator comes out saying "the number you have dialed is not in service".

I DO NOT RECOGNIZE THIS NUMBER

I do not recognize this number, but I have been getting alot of calls from telemarketers lately.

Numerous calls received from this number no clue what its for