I’ve never seen anything in the Catholic literature about “knowing” your guardian angel’s name. However, Mother Angelica suggests giving your angel a name (sort of like a supernatural FR handle ;-), so maybe that’s what your friends meant.
My angel’s name is Amparo, which means “helper” in Spanish.
God Created the Angels as Individual, Immortal Spirits with Intelligence and Free Will
The Angels in Sacred Scripture
Angels in the History of the Church
Angels - in Heaven, on Earth and in Hell
Catholic Q&A: Angels and Demons (Fr. Thomas J. Euteneuer)
Question: “Are there really such things as guardian angels?”