from amazons website-
Cingular
Here are the steps to transfer your current number to your new Cingular service:
Please Note: Transferring your number with Cingular is only valid for a new line of service when porting from another carrier. Transferring an existing number with Cingular will make you ineligible for Amazon-funded rebates. Your price paid includes an equipment discount of $250 that has been provided to you in exchange for either activating a new, non-substitute line of service or renewing an existing line of service with Cingular, and your agreement that for the 181-day period following such activation or renewal you will not use this line of service to replace an existing account with Cingular. If this condition is not met, you credit card will be charged $250 as reimbursement of this equipment discount.
1. Continue active service on the number that you wish to transfer to Cingular. There is no need to contact your old service provider. The old service provider will automatically cancel the service as part of the number transfer process.
2. Buy a new Cingular phone and Cingular service plan at Amazon.com. Your phone will arrive activated with a new Cingular number. Until your number transfer is complete, you will have use of both your old handset and your new Cingular handset.
3. To start the number transfer process, call Cingular at (888) 898-7685. Tell the Cingular representative that you have activated a Cingular number through Amazon.com and that you would like to transfer your number to Cingular from another service provider. Make sure that you have a copy of your most recent monthly bill from your existing carrier when you call Cingular. If you don't have a copy of your bill, be sure to provide the exact details of your account, such as your name as it appears on the bill, your billing address, account number, and current phone number.
4. Cingular will check your eligibility and, if you qualify, they will process your request. Cingular will explain the number transfer process to you in more detail; however, once the number has been successfully transferred to your Cingular account, the original Cingular number that was activated through Amazon will be replaced by the number you transferred.
5. When the number transfer is complete, your old service provider will cancel your account in their records.