I've tested it with other connection (Airport) running... I don't think there is an issue with that (** twho knows).
In the menu line on top of the screen, the connection status must show (if you select the option in the menu) something like:
- "Connecting..."
then the Terminal box appears, type the command (ATD*98#) and press "return"... do NOT press the "Continue" or "Next" button (the connection fails in that case).
- then you have "Authentication..."
- then, when it's ok you have the counter.
When does it fail?
Mr Ben