My dear son, err .... daughter.

This is your King and Emperor Charles V of the Holy Roman Empire speaking. Why hath you called for me? Are you in danger from Heretics? Or from Moors? Or from the French?

Observe my magnificent Habsburg chin, for I am the true Charles V, as King, Emperor, Duke, Count, Marquis, etc etc etc etc.

I can go into details as to the possible and likely circumstances surrounding Joan's fabled recognition of the future Charles VII, but I'm not sure whether it would be a waste of time...?