It's customary to include the breed line name(s) or kennel name in the registered name. For example, my female Sheltie comes from the breeding line called Arctic. Her name is Arctic Morning Mist.....call name Misty.
When my mom used to show, she never got to pick the names of the dogs. The breeder would maybe let her help name, but the kennel name(s) or lineages of the dogs involved in the mating would end up being the dog's name.
For example, if you got a dog from mating between Keeshee kennels and Trumpet kennels, you may end up with Trumpet's Fantasy at Keeshee or some such name or Keeshee's Sweetsong with Trumpet, depending on how the breeding is done.
This is just an example, and in no way is an actual breeding done. The kennels are real, however. Please don't sue me! LOL! ;-)
I think you only get a limited amount of letters, though.
You could of course pick the call name, like "Melody" or "Fantasia" or whatever you choose.