I had a player come into live today, their account had been closed due to an inappropriate alias. I informed them the reason and asked for the alias they would like to change it to. I created a csr note with the old alias "alias changed from xxxx as it was inappropriate for chat, new alias is xxxx" 

Then on the left pane under players there is an option "change player alias" click this and put the new alias into the box and update.