Change carrier text without jailbreak
Here's a relatively simple method that does involve jailbreak but ends up with a non-jailbroken iPod and a fake carrier setting.


Jailbreak your iPhone (stay with me)
Download Cydia App: 'MakeItMine' by Erika Sadun
Change the carrier name
Connect your iPod and create a backup on iTunes
Restore your iPod to factory settings
Restore your backup


Your iPod touch should now display your fake carrier and be non-jailbroken.