Barely 5 Mbps Uploads

I've been going on and off with chat, with several agents and getting absolutely nowhere.

They've reset my modem and I've done it myself several times, checked ports, turned off all firewalls, connected directly to my modem and eventually even upgrade my modem, but every single night, between 8 PM until around 12 PM, my upload speed is either 0.05 Mbps or a flat 5.0 Mbps.

My plan advertises 300/30 and I am indeed getting 290-300 download but almost never get 20-30 uploads.

During the very first month of this plan, it stayed at 20-30 Mbps with uploads, but after the first two weeks, it began to chip down until it reached where I am at.

Any advise on what else I can do?