Should I have received an upgraded router?

When I upgraded to fiber (300), the customer service rep said that the tech would put in an upgraded router. He did not - he said the current one (589) was fine. A few months later, I am just not getting the kind of speed I expected. The speed test that the auto assistant runs is always within the speed I'm paying for (of course) but reliable speed tests from other places get speeds that are unbelievably slow. As I look at the forum, seems that the 589 is out of date. So can the 589 handle the fiber upgrade or not? And how do I get an upgrade without buying it, since it should've come with the fiber installation?