So I sold my 8gb version on ebay and will be unlocking it using ziphone for the buyer and shipping it off tomorrow or tuesday. Meanwhile I'm waiting for apple to stock the 16GB in the stores (locally in CA they are out). Once I unlock it w/ my SIM card installed and then test it out with a TMO sim that I have and it works, should I then be able to take the ATT SIM card out and wait to get the 16GB version and install it in that? Figure the ATT sim won't be in use for about a week as I transition phones but didn't want the unlocked 8GB version i have to be useless for the new buyer. Thanks all..