I spoke with 3 different tech support agents over the phone. None of them knew what I was talking about changing the service code. you have to speak with the sales dept for them to change it. for some reason tech support does not have that capability.
Thanks for this post. I too was stuck at about 30ish down. Tech Support changed my service code. As you mentioned, they didn't have my service set to premiere docsis 3.
EDIT: I still seem to be capped consistently between 30-32mbps down, but upload is way better--something like 20mbps, and the perceived (didn't notice high ping times or packet loss) browsing latency has disappeared. I still see some channels aren't in use on my modem, so I might need to reboot the modem again or call Support tomorrow.