Upgraded to Ultrafast but still seeing old download speeds

Hi
I upgraded online to Ultrafast plan (900MB/s download) and I got a confirmation email but I am still seeing old download speeds of <100MB/s. Here is some detailed info:

• I have a Arris Surfboard SBG7600AC2 router+wifi and it can support 1G+ of speeds.
• I have tried both wired and wireless speed tests and I get the same speeds.
• I have restarted the modem from xfinity and also manually multiple times and still get the same low speeds
• The email confirmation does not say the plan is activated, but when I login to my account it shows the new plan.

Is there anything else I can do to activate this? I can't get a live person on Xfinity