In your original post, you transitioned from slow wireless to your connection with Cox. Although both connections (Cox Internet (WAN) & wireless) are housed in the same device (MG7550), there is a dividing line between the 2 connections. Cox owns 1 side and you own the other.
Cox and the tech said your WAN connection is fine, so focus on the wireless side.
Multiple things can cause slow wireless.
How many devices are on your wireless?
Are there any walls between the devices and router?
How far are the devices from the router?
Considering your router and your neighbors' routers, your 2.4 GHz channel may be too congested. You could switch your WiFi to a clearer channel.
2.4 GHz is not just one channel but is divided into 14 channels. That "2.4" actually has 2 more digits to further increment your frequency into the thousandths: 2.4xx. Frequency 2.4xx starts at 2.412 and ends at 2.484. However, North American doesn't use 3 of those channels, so it's actually 11 channels.
Anyway, you can try to find a clearer (less congested) channel. WirelessNetView is a good program to scan for a cleaner channel in your neighborhood. I'm sure other contributors may recommend better programs.