Cox sporadic internet service.

I quit cox tv, and went with a steaming service,(roku), or online with my computer, or ota signals. Recently I,(stupidly), followed cox advice, and got a cox modem, to replace the modem and router. Now I spend several minutes everyday trying to get the roku to connect with the cox modem/router. When I explained the problem to cox, I was told that the best plan, was to buy a NEW CABLE TV PLAN FROM COX, and that it would only be an additional $72.00 a month. When I informed the representative, that the issue DID NOT START UNTIL AFTER I STARTED USING COX EQUIPMENT, the representative suggested a new internet plan, and an additional cable tv plan, that would only raise my monthly by $120.00.