I have a new callsign.

It wasn't the one I had thought was so original. (Grumpy) It wasn't any of the dozen or so that I came up with when Grumpy was taken. (they were all taken too) It is a callsign that I see as being woefully appropriate: "Silkmonger". (since that's what I'm so frequently flying)

The lesson I learned from this? Do not go near the feature that allows you to blow your one free callsign change if you're less than 100% alert, and have the new callsign (and several alternates you like) before you start. Go ahead and make a deal with yourself not to keep trying new ones if the ones you like are all taken, before you start into this.

Now, how do I change my callsign in here to match my new in-game callsign?

It has been changed!