I think they want your social security number. Cos everytime i call ATT for my girls iphone they verify the last 4 of her social. And I am Tmobile and have a blackberry they also do the same.
But i found a back dated article
http://reviews.cnet.com/8301-19512_7-10115601-233.html
regarding the iphone requiring social security #. Although i also read this.
4. I tried to open a new account with a private business, but the business requires my Social Security number. They say they will not do business with me without the number. I do not want to give it out. What are my rights?
Usually you are not legally compelled to provide your Social Security number to private businesses unless you are involved in a transaction in which the Internal Revenue Service requires notification. The Patriot Act requires financial institutions to verify customers’ identities, which can involve the SSN.
There is no law, however, that prevents businesses from requesting your SSN, and there are few restrictions on what businesses can do with it. But even though you are not legally required to disclose your SSN, the business does not have to provide you with service if you refuse to release it. So in a sense, you are strong-armed into giving your SSN. This is often the case when applying for insurance and opening utility accounts.
But don’t give up. Be sure to ask if there is an alternate number that you can provide to the company, such as your driver’s license number. Also ask if you can provide a deposit rather than giving your SSN to the company.
For more information and on advice for dealing with these situations see Fact Sheet 10 www.privacyrights.org/fs/fs10-ssn.htm