"Sam is a doctor."
If you wanna call him, simply say it in the same order as in English, "دكتور سام"
I assume you'd put a يا in front to indicate that you're addressing Dr. Sam, so:
يا دكتور(ة) سَم
depending on if it's a Dr. Samuel or a Dr. Samantha.
I read through the discussion here. My question: In English the name Sam can be for both males and females (short for Samantha). If Sam here were a female doctor, how would that change دُكتور ? Thanks. Also, is this English calque as common as الطبيب? Thanks. [I got the latter word off of google translate]