You can change your name on one occasion only and I believe it will cost you A$2,500
You can do this by sending your request via Support on the menu bar, top of this page.
Achat will debit your account once it is done.
I do believe however your friends and ignore list will not transfer over, so make a note so you can add to your new named avi account.
You cannot delete old Achat accounts, however after about 6 weeks inactivity, the account will disappear from the game.
Accounts that have never been paid for will be automatically deleted by Achat.
Accounts that have been paid for on at least one occasion can be reactivated by just logging in again.
So if you want the account to remain inactive, just dont log in.