How to know how much data I have left in mr attnt iPhone?

How do I know how much data I have left in mr attnt iPhone?

Some of the nation's largest wireless phone companies are getting around those plans by slowing down a smartphone's Internet transfer speeds for heavy users. The practice serves as a backdoor limit of data by making some downloads impossible.

The wireless companies say they are trying to find a fair way to manage the swelling demand for mobile data, but consumers are feeling cheated and suspect some carriers are trying to lure them into higher-cost data plans.

If I use home Wi-Fi will it use up my data time?