By Marina Lopes NEW YORK (Reuters) – Increasingly aggressive discounting is taking a toll on ATT Inc and U.S. cellular rivals as they struggle to attract customers in a nearly saturated market. While recent price cuts by ATT led to a surge in first-quarter subscriber adds that beat Wall Street expectations, average revenue per user fell, triggering a 3.2 percent share drop. Other wireless carriers shares also declined, with T-Mobile US Inc, which has roiled the industry with a series of discounts and new pricing plans, down 2.8 percent. ATTs result and the share fallout is the latest sign of how U.S. cellular phone providers, once seen as companies with strong growth potential, are having to resort to discounting in a bid to retain or lure clients.