There is a new Cydia tweak, named AskToCall to which you will be asked each time you want to make a phone call.
You need to firstly click “Call” button to confirm that you really want to call someone.
If you don’t want your iPhone makes the unwanted phone call without your notice, because of technical reasons then AskToCall is your rescuer. You can get this app for free in Cydia under BigBoss repository and your iPhone must be using iOS 4.0 or higer

