You can't get rid of the "Alpha Black" stuff. You can change it to "Bravo Green" or whatever you like, but it is always there.
You can have two special callsigns, of which one is usually Papa Bear. There is a tute in the Ed Depot on how to change that to whatever you want.
If you want more than two, then the workaround is to start the message with the callsign you want.
"(Sgt Smith) - Ready when you are, boys."