Here's an idea for all the people with phones that have BL4.6, TRADE it with someone that has a BL3.9 that is subscribed to ATT.
There are many "legit" iPhones with ATT on BL3.9 out there. If you offer them a brand new OTB iphone for their "old" phone, they will TRADE it. They get a brand new phone an you have an "old" phone that you can hack.
Just an idea ........ :)