Here is some more info about problems with outgoing calls.

I have a US 1.1.2 iphone activated, jailbroken and with a Black Stealthsim.

All functions run smoothly, including SMS, incoming calls, iTunes, etc.

When I am in my home country (Luxembourg), the outgoing calls work fine. When I go abroad (in France), I still receive calls but I CANNOT make outgoing calls. The following happens:
- I dial the number (either via dialpad or from Contacts)
- iPhone goes calling
- I do not get the usual "Call Forwarding / Dismiss" message (which I usually get when calling from my home country)
- Then I get a screen like an incoming call from the number I dialed. This call is treated like a 2nd call (see multiple calls). I can either Dismiss, which yields a "Call failed - Call Back / Cancel" screen, or Answer. If I answer, the call fails seconds later and the person I am calling does not hear nothing and in fact is talking to my Voicemail : I receive a message some times later with the person trying to talk to me ( "Hello?...hello?...")

Another hint, I dont know if it matters: I use iWorld. When set to Luxembourg, I get all the behaviour above.
When set to France, I simply cannot dial: as soon as I press one digit or one contact, the iPhone jumps back to the springboard (NB: original sprinboard). I had this problem systematically before I installed iWorld.

I have been searching through forums for days now. I would die for some help!

NB: I posted this same request on an existing thread but according to the answers it might have been a bit confuding (apparently different subjects). I did not see any similar problem in my search, that's why I start a new thread.