Getting a callsign doesn't actually mean ATC will use it!!!
You'll be given a three letter code, say, xbc, which will then be referenced by ICAO as NewBoy or whatever you wish to be called. It of course must be a sensible word. But ATC won't necessarily know, without looking at a flightplan strip that XBC1 should be called 'NewBoy One'. It is only through familiarity that ATC know to call flight BA012 'Speedbird Twelve'.
So you'll have to file a flight plan with the correct registration on it, with a remark that XBC should be pronounced NewBoy, and even then you'll be called XBC One by most ATCs. We know by experience this happened for our AOC operation, such that it was easier to revert to the registration.
Even the larger FTOs which have callsigns only have them used by ATC that are familiar with the reference when they see their short code displayed.
Now why do you want to waste all that time and effort getting a callsign?