I kinda like it. Where he got the impression that it's my real name from is beyond me, but I'm not gonna question it. It's nice to be greeted every morning with a cheery 'Morning Jeff!'. Even if your name isn't Jeff.
I might greet him back with a cheery 'Hello Roger!'. I don't know if this is his name, but I like to think it will make him happy as well. Fake names > real names.