Netgear CM2000 + XR1000 = poor upload speed

Was previously on the "Faster" internet plan with advertised speeds of 800 down 24 up. Promo pricing ended and I switched to the newer "Fast" internet plan because their advertised speeds are 500 down 100 up. I've restarted and power cycled both my modem and router it seems like a dozen times and I am still only seeing 24 upload. I've chatted with 5 different Xfinity chat agents over the course of a week and they all say the same thing, "please restart your modem as I have reset the signal". From what I've read online both my modem and router are far capable of +100 upload speeds. Why am I not receiving the advertised speed or remotely close to it?

Note: I am not tech savvy. All my previous internet related issues in the past have been solved with power cycling my modem and router, or xfinity resetting signal.

Location: Spokane, WA