My mother calls me Ronnie, my son and daughter call me Dad, my wife calls me Bubba. You can call me whatever you want (mostly it’s just Ron). If someone calls me by a different name it has no effect on who I am, but if someone starts describing me and says I am short with green eyes and my primary language is Italian THEY DO NOT KNOW ME.
To know me is to know me. I am who I am.
When someone tells you they know God, ask them to describe him. What is he like? How did they get to know him? What pleases him? What allows them to stay in a good relationship with him? You can find out what God they know by asking. Maybe they know the Great I AM, or maybe they only met a lesser god.