1. Hello, this is so-and-so. I got your message about the interview. If it\'s not a bad time we can do it now (or whatever).
2. Hello, I received a message from you regarding my getting back to you for a short conversation in English.
To me, whenever you choose to say \'your messege\' you believe they remember what they said and repeating it all word for word is like telling them what they already know (read: retarded). Using \'a message\' justifies, in a way, the full message description. But that\'s me, and me is but a humble happy hour.