Upgraded to 1gig internet, purchased new modem, no increase in speed

I just upgraded my plan from 300mb to 1gb 5 days ago. In turn, I had to upgrade my modem from an Arris SB6183 to an SB8200v3, so it would be DOCSIS 3.1 compliant.

the new modem works, but there has been no increase in speed on my asking. A tech already came out once and verified the cable is good and the modem is working, but speed is still only showing ~325 down. This is regardless of whether I use my wireless or gigabit Ethernet connected devices.

any help would be appreciated, because my last chat with support said I needed to upgrade to “advanced security”