Constantly losing connection

I run most of my devices wireless but even for devices that I have hardwired, I lose connection. I know it is not my modem/router because it is the most recent one from Cox. I lease it. I pay extra for the one they recommend because they said that the modem/router that I had which was the Arris Surfboard SB 6121 DOCSIS 3.0

was the problem. Now on top of the high price I pay for internet, I also pay extra for the modem/router they sent me. I still get latency or connection problems. I had a tech come out and check the wires. He changed out all the connections at my house and at the terminal in the street. He said they were bad. He said all he could do, he did. If the problem persisted, it was my modem. It was new. I still decided to go with the cox modem. I lose connection to my printer, I have to get it back on to wireless connection. I lose connection to directtv and it is hardwired. I cannot even play my PS2 because I play online and when I start a session, it times out in the middle. Not even one game gets finished. I just turn it off. It it not good because Cox offers the highest DL and upload speeds and if I change providers, I lose out on that. But it means nothing if I cannot stay connected. The tech that came out, looked at my settings. I logged into the modem and he said everything looked good. The rep said I should go to a higher speed so I did and still not fixed. What else is there to do?