Even Elliott Management has had enough of AT&T. The activist investor has divested some $151 million in shares, just over a year after it gave the US operator an embarrassing public beating. Despite this sale of shares being pittance from the total $3.2 billion slice of AT&T that Elliott Management owns through various funds, the worrying thing is that if Elliott has already started calling it quits by selling shares for less than it paid, long before AT&T’s stock price has made any sign of recovery, then the investment giant clearly sees no way up for AT&T. Despite AT&T’s initial reticence, it eventually began taking onboard lessons from Elliott Management by gradually selling off assets. Perhaps Elliott is trying to…