Free ATT ringtones are the way you can personalize your cell phone with hot new music hits. Not all mobile carriers can offer free ringtones to its customers, but the question is not about carrier but about mobile content provider. Most of all mobile content providers offer ringtone subscription services, for a fixed amount of money you will get credits which you can redeem to free ringtones, wallpapers, mobile games and text services. The price is usually about $10 per subscription per month and is billed right from your cell phone, so you don't need any credit card to subscribe.
Free ringtones for ATT may also be sent to your phone if you subscribe to unlimited ringtone plans with mobile content providers using your credit card and pay $10-15 a month for a possibility to download for free unlimited amount of ringtones.