I can remember a zombie talks on the phone to people in a house, and tells them it is all clear, and to come on out. They ask him who the current president is.
Return of the Living Dead Part II (TV Tropes link)
A particularly clever zombie almost lures the protagonists into a trap, until Dr. Mandel asks him who the current president is. Having been dead for years, if not decades, he has no idea
Found with a search for film zombie telephone "current president"