How can I get Charter to fix my internet speed?

I'm paying for 30MB/4MB. It usually stays in that range from 7AM til about 7PM, then, at around 7PM, my internet speed drops from the normal speed down to 0.25 - 3MB The upload speed stays the same. I had just about every single member of the god dam technician team to come out here at least 2x. None of them could find what the issue was because they can't make it out after 7PM, which is when the problem usually starts. So....how can I get them to actually fix this? It CAN'T be because of too many people using the internet because its happening EVERY SINGLE DAY. My speed test at 7PM : [att=1]