Internet Speeds Capped for Months

I have been paying for Gigablast internet for just about a year now, but the last 3-4 months my WiFi speeds have been capped at just under 300mb/s. I called Cox Support a couple times when it began and all I was told was that the nodes are "oversaturated" from increased data usage of nearby people. It's been months now and I still get the exact results, landing in at 294-299mb/s on multiple speed test websites. I've removed all other connected devices, use only ethernet, and reset my modem multiple times.

So why am I paying $110 for Gigablast internet and getting a third of the speed? I would be happy if I was paying a lower price for this speed, but $110 every month is a lot out of my pocket for this speed. How can I ensure I get better speeds, or pay less for this speed I'm currently recieving?