AT&T announced it will start slowing speed for mobile users who exceed 3GB/month, citing rising mobile traffic has been limiting its network capacity. The wireless carrier received piles of customer complaints about slowing data speed and hopes this announcement will offer clarity. CEO Randall Stephenson said the company expected the T-Mobile acquisition would add network capacity, but the regulatory opposition to the deal left AT&T with less time for network expansion.All national carriers are facing the network squeeze. Verizon Wireless ended the unlimited data offering last July and took away the long running New Every Two discount on phones. T-Mobile canceled the unlimited data plan in April 2011. Sprint remains the only one with unlimited data available for new customers.