Really Simple answer what this is.  It's a Medicare Scam.
He asked me if I was "Doug".  The next thing he wanted was my medical coverage / Medicare info so he could get me my back pain pills.
Except I don't have back pain.
BUT understand that, some of those pills are quite effective narcotics, so Some people might be interested for that reason alone.
I asked to be put on their do not call list but the call cut off after I said " put me on your do..."
I guess they hear that a lot.