I was just looking at some numbers here... On my telecom.co.nz account page I see:

As at 02 Sep 10:21am
376.60MB / 500MB

On my smartphone I use the sphone.telecom.co.nz site and it shows:

As at 02 Sep 10:55am
408.50 MB / 500 MB

That is an incredible difference for 30 minutes, knowing the phone was on the charger, not being used, and I don't have any automatic sync going on...

I know it's not real time, but two different numbers from Telecom "official" pages...