Are Andrei & Andrew the same person? (Andrew's version)
Ok - so, explanation time: Many Russian immigrants choose what "American" name they want to use when speaking English. Those with the Russian name "Andrei/Andrey" typically choose, Andrei, Andrey, Andre or the Americanized Andrew.
Andrew chose Andrew (or maybe his parent's chose it), so when speaking in English he goes by Andrew. When speaking Russian, or when with his Russian friends, he goes by Andrei (with a rolled "r").
Long story short - feel free to say Andrew, or if you can roll your "r" say Andrei!