Rebel + 3G + incoming works.... for a while...
For the record, i tried to follow those instructions I found:
Got to Settings and switch 3G off, airplane mode on, Data Roaming on
Switch iPhone off and remove O2 SIM
While non-O2 SIM is in its original phone force the phone to Manual Network selection
Choose any other network than the original for that SIM and allow it to reject
Immediately switch off the phone and remove the SIM - do not go back to any other menus that may cause the phone to automatically re-attach to its parent network
Remove the non-O2 SIM
Fit the non-O2 SIM and Rebel Simcard into the iPhone
Power up the iPhone
Got to Settings and switch airplane mode off - it will pop up a message about the SIM being invalid or suchlike, just acknowledge it, wait for network to lock in
You may have to toggle airplane mode a few times to make the previous step work
Go to Settings : General : Network : Cellular Data Network and enter the APN settings (see below)
Step back to Network and set Data Roaming to On
Once it is synch'ed make a phone call, the other party does not have to answer
Start Safari and browse in 2G
Go back to settings and switch to 3G
Make a phone call, don't need an answer
Start Safari and browse in 3G
Thats it job done
And It worked.
I had 3G enabled, and could receive calls - no problems.
I was very happy, until I tried again an hour later and incoming calls went straight back to vmail. (whithout changing location so I assume I still was on the same cell) (FW: V61i)
The positive news is that it can work, we just need to find out how to make it last.