You could start with "I'm doing genealogical research..."

Me: Hello?
Lady: Jennifer?
Me: Yes?
Lady: Is your middle initial T?
Me: Who is this?
Lady: I'm looking for Jennifer with a middle initial T.
Me: That's not me.
Lady: You weren't born in 1980?
Me: No
Lady: Ok. Sorry to bother, goodbye.
Me: Bye.

Hah.