I have a friends phone that is on 3.1.3 and already working on T Mobile.. what can i do to upgrade it to 4.0 for them and not loose the unlock and JB? firmware is 04.26.08 model number is MB702LL I just did one that was on 3.1.2 with snowbreeze and that worked great so what works on 3.1.3 same thing or something else?