Comment 2 for bug 1287267

Monitoring data usage is not a feature supported by oFono ( or rild for that matter ). NetworkManager uses oFono to activate the cellular data connection, and then it sets up a default route for the device. As none of the actual network traffic flows through oFono ( or NM ) itself, it's not really something that oFono can provide.

This kind of data tracking needs to be done via direct monitoring of the actual network interfaces via the kernel /proc or /sysfs.