AT&T has tried to match Sprint in the marketplace as a price leader in data plans. But a new report today reveals that the U.S. mobile giant is using limitations and data “throttling” once users reach a data usage threshold, possibly shuttling subscribers to Sprint once the 4G iPhone 5 is released.Anyone who uses a smartphone has had to make themselves aware of the pricing games that mobile carriers play with users when it comes to data usage. Sprint, America’s third-largest mobile carrier,...