I bought my son a 8300 on ebay about 6 weeks ago. Paid to have it unlocked so it would work on t-mobile. The phone is working fine the only thing that is wrong with it, is when your reboot the phone you get the AT&T logo. I can't fiqure out how to get it to reboot with no logo or t-mobile logo. It not really a problem but if someone knows how to change it please let me know Thanks

You cannot change the splash screen.

The unlocking only allows you to use SIM cards from a different mobile provider. It does not affect the logo you see. As far as that go there's nothing you can do about it unfortunately.