U.S. regulators are calling out AT&T and Verizon for exempting their own video apps from data caps on customers' smartphones. The FCC has sent letters to the country's biggest wireless carriers saying the way they handle the practice, known as "zero rating," can hurt competition and consumers. From a report on ZDNet: AT&T launched DirecTV Now earlier this week. AT&T Mobility customers can stream video data over LTE without impacting their data allowance. Verizon offers something similar with its go90 service. AT&T and Verizon don't see any wrongdoing. In a statement Friday, AT&T said exempting services like DirecTV Now from data caps saves customers money. Verizon said its practices are good for consumers and comply with regulations. "We will provide the FCC with additional information on why the government should not take away a service that saves consumers money," AT&T wrote in a statement Friday. The FCC hasn't released any official ruling on "zero rating," just guidance. It said on Thursday a similar letter was sent to AT&T in November, but the FCC didn't like AT&T's original response.