Slow at night

I am starting to believe that cox slows my internet down at night on purpose. I work nights so when I get off I cant even play my games let alone use the internet. I ran the speedtest on the cox website and it timed out.!!! I have tried wired and wireless. They claim fastest in home wifi, but i dont belive this for a second. I know people with verizon and they dont get these problems. I pay good money for this internet and talk about useless. It has been 4 months of useless internet at night. works fine during the day. I am so angry that I would switch internet if I could. the only time this internet worked was the day the installer set it up.