I am not a native English speaker and use the expression "come again" in various forms such as "Come again, please" or "Can you come again?". I consider it to be a general expression which can also be used in formal speak. Is it not the case?
In my search for the answer I read through this question that discusses the sexual connotation of the phrase. But I could not definitively figure out if the expression can be used in a formal sense.
How does it fare compared to using "Pardon" or "Sorry" in the same context?