Internet plan upgraded but speeds have not changed.

3 months ago we upgraded our internet plan from 200 mbps to 800 mbps but the speeds have not changed. Also, in various spots on the mobile app and Xfinity.com, it shows our plan still at 200 mbps. If I run a speed test from Xfinity's mobile app it still shows we are being run against the 200 mbps plan. Customer support hasn't been able to assist other than suggesting I change my modem to their rented modem. Currently using a MB8600 which is be plenty enough for this increase. The issue seems to stem from the plan not getting fully switched and it not a hardware issue on my end. But yet again, they are sending out a technician to "diagnose" my lines. If the plan is still showing 200 mbps, the lines and hardware are not the issue. Can a company rep please look into this issue?

Mobile speeds are faster (but show the 200 mbps plan) but when running on PC's and Mac's I am limited to under 200 mbps.