3GS, iOS 4.0 - "Phone" does not work, and I cannot send texts unless I have 3G on

[jb7]

Anyone know why this is? I currently have a five bars of reception, can send/receive texts, and make calls. If I turn 3G OFF, I get 0 bars of reception. I cannot make calls, and if I try to send a text, it says message failed. The only way to fix this is to turn on 3G, and then reboot. If I just turn 3G back on (without rebooting).. the situation remains the same

Any idea how to fix this? Network = 02 UK

thanks

 

[abijnk]

When you upgraded to iOS 4 did you restore from a backup? If so I would recommend restoring and setting up as a new phone.