If your phone is jailbroken, there's application you can download/buy from Cydia to keep track of your data.

This is my first post here. I'm not sure if jailbreak topic is allowed. Please kindly remove my post if it's not allowed.

By the way, I'm bringing an Iphone 4 back from USA and I was wondering if I can get into one of those Iphone plans offered by Maxis or there is another plan for customers who already have their own Iphone.

Thank you in advance for the answer.