I have some questions about the difference between 係 and 担当.
Do these words have the same meaning? Basically, can they be used interchangeably as "the person/group in charge of something"?
I know that there can be more than one 係 in a department (for example, when sending an email, it seems like 経理係 御中 is acceptable), but can there be more than one 担当? Or does 担当 only point to one person within a department? On a similar note, if you don't know who the person in charge is, should you write ～担当 御中 or ～担当者 様?