If you’ve been thinking of using FaceTime over a cellular data connection, you may find it useful to keep an eye on how much data a given FaceTime call actually consumes. When Apple added the ability to use FaceTime over Cellular in iOS 6, it also quietly introduced data usage indicators to the Recent Calls list in the Phone and FaceTime apps. To see how much data a FaceTime call has used, simply go into the Phone app on your iPhone or the FaceTime…