Currently Being ModeratedJan 4, 2013 10:16 AM (in response to JimSo)
Downgrading is not possible. Attempting to do so will void any warranty and forfeit your right to support.
What carrier are you attempting to use? AT&T is the only supported GSM carrier in the US.
Currently Being ModeratedJan 4, 2013 1:57 PM (in response to JimSo)
Straighttalk piggybacks on the AT&T network. The phone thinks it is on AT&T and will not allow you to change the settings because it believes there is no need to.
Search these forums or Google. I believe you will need to insert a different carriers SIM (e.g. T-Mobile) before those options will appear.