Just an fyi for the german people coming in via google looking for the 1.1.2 jailbreak:
If you happen to have a german T-Mobile iPhone and already did a jailbreak (by downgrading, patching, upgrading) you might have noticed that your Visual Voicemail doesn't work anymore and that t-mobile starts billing you a bunch of money for your GPRS traffic.
That's because of the APN (kind of the "access point"; for GPRS) that is set when doing the whole procedure necessary for the jailbreak.
Apparently the "official"; APN is set instead of the "new iPhone";-APN that is used. That does make sense for all foreign iPhone users that come to germany and would not be able to use the "new iPhone";-APN because they haven't got the t-mobile germany contract. With the "official"; APN they could use their providers usual roaming.
These wrong settings are most probably also the cause for the clock not working correctly and the Visual Voicemail Service not functioning.
So if you happen to be one of the guys who did the jailbreak: reset your iPhone! (Something in "Einstellungen —> Allgemein —> Zur√ºcksetzen"; … don't really know which one).
Visual Voicemail should start working and Edge will be "free"; again.
alternatively you could try resetting it the "shell way";:
ln -s /System/Library/Frameworks/CoreTelephony.framework/Support/TMobile_Germany.plist /var/root/Library/Preferences/com.apple.carrier.plist
rm -f /var/root/Library/Preferences/SystemConfiguration/preferences.plist
Not sure if that definately solves the APN Problem 100%… I'd check my "mein T-Mobile"; section or give "2000"; a call and say "details";
p.s. as usual: i might not know what I'm talking about, so do that stuff on your own risk!