Internet speed 1.2gbs instead of 2gbs

I upgraded my plan to 2gb and installed a new Xfinity modem xb8. When I use the Xfinity app it says I am on 1.2 gb plan. I am getting 1400 to the modem using their test. I have never gotten over 40gb upload speed. I have gone on chat twice recently and they could not correct it even after following all their steps. Any help would be appreciated. I not using an external router. The system is working I would just like to get the higher speed.