How do you change your ringtone on the iPhone 3GS without using iTunes?
You can't unless you can find a app at the app store that can do so, otherwise you will need to jailbreak your phone that's the only way unless you want to pay for it or plug it to computer everytime
The iphone is a gimic to get you to buy a computer
The App Store has a lot of apps for free ringtones. Just go to the App Store and search "free ringtones".