Talking to him, I would say (like YesorNo & APushataYid), “I want to ask The Rov …”
Talking about him, I would say, “The Rov said…”, if there was another Rabbi Ginsburg, “Reb Eliyohu (Ginsburg – if there is more than one Rabbi called Eliyohu) said…” I’ve been told that in America, the equivalent of Reb Eliyohu, would be Rav Eliyohu.
Here in Manchester, there are two Rabonim with the exact same name. Let’s say for example it’s Rabbi Binyomin Greenberg. One is a Rov of a shul, the other is the mashgiach of a Yeshiva. (They happen to be mechutonim as well, but that’s for another time). The one who is a Rov, has a nickname, let’s say it’s Benny. So people will say, “I spoke to Reb Binyomin Greenberg today, I mean Reb Benny, and…” adding in the nickname for clarity. If they mean the other one, they will say “I spoke to Reb Binyomin Greenberg today, I mean the mashgiach/ the one from Shaarei Torah, and…”. In this case the nickname is used purely for clarity and does not demean the Rov in any way.