AT&T won't be matching T-Mobile's offer of free wireless data for the iPad Air when the device debuts at the company's stores across the U.S. next month.AT&T, the country's second-largest cellular carrier, said it will offer a US$100 discount to customers who sign a two-year contract for tablet data service.For customers who don't want to sign a contract, AT&T will offer recently announced plans costing between $5 for 250MB of data for one day and $50 for 5GB for one month. Those customers won't get the $100 discount.Subscribers will also be able to add the iPad Air to an existing data plan for an additional $10 per month.On Wednesday, T-Mobile said it will give tablet owners 200MB of data per month for no cost. Once that's used up, customers will have the option of paying $5 for 500MB of data for one day or $10 for 1GB of data for a week.T-Mobile,
