"Call Ended" immediately after dialling number (iPhone 5)
When I try to make a phonecall, either by dialling the number or by picking a number from my contact's list, I immediately get "Call Ended". My iPhone doesn't even start dialling the number. This is usually fixed (temporarily) by rebooting the phone. This is rather annoying and scouring through Google didn't yield any results so I thought I'd try my luck here. Any help would be greatly aprreciated!
iPhone 5, iOS 6.0.1, Carrier: Telenet (BE)