inconsistent download speeds throttling down

I have had Cox for about two years now. I have paid for the one gig service and rarely did speed test in those two years. I understand the construction on Gulf Beach Highway may have had some effect on outages and even though they were sometimes for several days. However, my modem went out just recently and I went round and went round trying to get it working until I purchased a new high-speed modem and spent a ridiculous amount of time trying to get it registered since the site on Cox app does not allow for registration and sends you round and round for hours.

However my point tonight is with my new modem I've been doing speed checks Speedtest and trying to make sure that the modem is not the problem. I have noticed that for my one gig service (and I have hooked up with ethernet from my computer to the modem ) that there seems to be a throttling down after 5:30 and definitely after 7 PM until at least four in the morning of my one gig service to 28 or so megabytes per second with the upload very poor also one megabyte possibly. I don't know what's going on I would like to be able to find out if it is something technical or if they normally throttled down during the off hours. Then why should I pay for one gig service if I'm up late at night wanting to stream or wanting to download an update for apple says it's going to take three days. Are we back in dial-up mode? This is unacceptable but I know of nowhere or no one to talk to to find out what's going on with Cox cable regarding this. It's very frustrating I have the proof I can show you my Speedtest log that verifies this very fact.

Since Cox is the only girl in town at this point it's hard to make a switch to another provider ISP. So this seems to be the only place I can complain and be really robbed of being charged for one gig and getting only 28 MB. From 4 AM during working hours I can get between 300 and 600 which is acceptable given the devices I have.

 what gives anyone else having this problem? And does anybody from Cox have an explanation?