About a couple of months ago I installed an app called Onavo that can track data usage for each service or app running on your phone. One of the apps/services that has surprised me with the amount of data usage is the Phone service. For example this month it is reporting that the Phone service has used 386MB of data. Why is it that the phone service is using so much data? I thought the voice was voice and did not run over the data network. Or what is it about the Phone service that is using so much data?