Whenever you buy a mobile from Cingular they usually lock your mobile for security and network reliability reasons so that all calls from Cingular are processed easily.  Later on if you wish to change your mobile phone network then you have to unlock your mobile phone so that it can work with other network service and you will need Cingular unlock for this.

You can do this and there is no violation of laws that phone cannot be unlocked by user unless your phone contract state that the company have right for ownership of phone. By unlocking your Cingular phone you can be able to use any other network with different facilities. By unlocking your phone network you can able to sell this mobile phone as well.

In order to unlock Cingular you should have unlock code because this is the only way you can use to unlock your mobile phone. There are different websites that can give you Cingular mobile unlock code that can help you to unlock your mobile instantly without any assistance and you will be able to unlock your mobile phone. You can even get this mobile code free of cost.

You can get your sim unlocked by using IMEI number and you just send your IMEI number to different companies and you will be able to get your mobile unlocked easily. You can just need to enter that special code to your mobile and your cell phone will be unlocked and you will get message for unlocked mobile.

Keep this code once you get it so that you can use it again in future if you ever need. However you can get it instantly by paying minor amount for unlock of your mobile. To get unlock codes of your mobile check out these links:

Cingular Unlock Code For Mobile
Get unlock code for your mobile to keep it working
agains.
http://www.cell-unlock.com/imei/cingular-imei-unlock.html