New Gigabit Upload Speed

Hi-

I recently updated to the "new" Gigabit plan, which claims to have download speed of 1000 Mbps and 150Mbps upload. I ran speed test and it shows around 20 Mbps, which is more or less the old plan (1000/25). I was wondering what could be the reason?

I have my own modem MB8611, which is DOCSIS 3.1 with 4 channel upstream and should be able to handle up to 800 Mbps up. It's also a supported device.

Could someone please suggest?