The attorneys general of 44 U.S. states and Washington D.C. on Wednesday asked the country's largest phone companies to install technology that would allow consumers to block automated telemarketing calls, known as robocalls. In a letter to the chief executives of AT&T Inc, CenturyLink Inc, Sprint Corp, T-Mobile USA Inc and Verizon Communications Inc, the attorneys general said a June 18 ruling by the Federal Communications Commission made clear there are no legal barriers to offering the technology.