All user names are in use

My son cant play online because all the user name are used. I have made some real hard ones and there all been used. I cant believe that ever user name has been used. Like wowyoyo1212 and it has been used. How do get online play if all the user name I have come up with are used. Is there a error in getting online to play? We paid 6.99 and we cant even register on user name.

&)(($@ about Modern Combat 3: Fallen Nation