4 GBs up/down is a lot to have accumulated in just a few weeks*... You have your device jailbroken it looks like (that's the only way to change the carrier name, right?) so maybe something is being naughty there?
Try resetting the device maybe? Or check your carrier's information, see if it matches up.
By comparison, on my 5, I have since Feb 5:
Sent: 195MB
Received: 2GB
And I do stream stuff, like, all-the-time.