Owners must have purchased their iPhone prior to August 22, 2007 and must activate their phone with AT&T prior to being eligible for the rebate.
Once the iPhone owner has entered their serial number and phone number into the Web form, an SMS text message will be sent to their phone with the access code to redeem the $100 credit.
Apple offered the credit to early adopters of the iPhone after Apple cut prices on the device by $200 just two months after its launch.
I like the simplicity of getting the credit ... I will use it today. I would have liked the option to use it for my AT&T bill though.