The aggent is bullshitting you. you have the right to choose pay by yourself or let insurance do it. by the way, the repair should be way higher than 300 enven for a normal brand, it could run from 600-800 for repaint the bumper. For a Benz, it could be higher but not as high as 2000. you have the right to let the benz ownner check price in more than two shop and pick a more resonable one.