Not sure if everyone knows or not but all IPhone 4's are un-networklocked and if your older Iphone is with Telstra and still network locked, it is now free to have it unlocked. Just call 1800 782 489. No more jailbreaking reqd .
I got a long list of things to do in 5 hours to finalise the unlock which i hope i have noted down properly, if any one else rings and unlocks can you check my list and add to it anything i missed.
Connect Iphone to PC with itunes open
go into summary
check for updates
Sync Iphone to Itunes
Switch off and remove and replace the SIM or try your new Non Telstra SIM
Should be done now
I hope i have all the steps right if i don't or have missed something out please, please correct me
It is handy to have your IMIE no ready before you call - get this by typing *#06# into you phone first
Cheers - john