Every iPhone is locked with AT&T service provider provided by the Apple Company. It is very expensive service provider as compared to other network provider. iPhone user who want to use different service provider first unlock the phone using iphone unlock software. There are number of site that provide unlock software for iPhone. You can also unlock your iphone using the IMEI code. Every iPhone comes with imei number which is the known as the identification of that iPhone. If you change that code then you will be ready to use different service provider.
You can find fifteen digit IMEI code on your iPhone under the battery. There is also some special code through which you can see in your screen. It is also registered in the Apple database. Changing the imei code means that you are no longer connected to the Apple database. It is not a legal process to unlock you iphone by imei code. If you want to unlock your iphone by changing your imei number then you can talk to other service provider. They will charge you some money and provide you another imei code on which you can use their services.
This process is bit expensive and also not safe. The best and safe process to unlock iphone is through unlocking software. You only have to download the software and follow the simple steps. There are some sites that provide unlock software but it does not offer full features. If you use this software your iphone will be relock to the AT&T service provider when you upgrade your iPhone. It is considered to buy an iphone unlock software from the authorized site which is giving money back guarantee. It will not keep your iphone unlock even if you update new firmware.
After unlocking you can use your favorite service provider which offer cheap call rates. You can save lots of money if you are a frequent flier because AT&T service provider charges high roaming call rates if you use from abroad.