Well there's a few things, you should probably migrate the account and then password change it. Just changing the password can mean nothing and if he really wants the account back he could get it.
Now as far as you owning it, well I don't really see why you would need it unbanned. With saying that I can probably hear the next comment being about the credits well....
OneManWo1fPac wrote:
1: Ael was kind enough when I asked for 20 seconds before he banned me, to allow me to have 20 seconds. Which I sold all my realms to roach. My only 2 realms left are dispensed realms I bought that I need to sell. I bet several people are waiting to get my triple skeleton grinder, already sold it to roach
for 1 credit
What's the excuse he didn't give you the credits if he had enough time to sell you the realms? Which shouldn't have been aloud to begin with.
With all that said, unbanning the account would just cause confusion among all players, yes you own it but not everyone is going to know that and flip out.