ARRIS SB8200 Modem levels too low. Internet Speed to Slow for Gigablast Plan I'm paying for

I been talking in circles with the cox customer support for days they say everything is fine on their end. I called ARRIS today and they said my signal levels were low on the modem and that's why I'm not getting the speed I'm paying for.  I finally convinced them to send a technician out after they in multiple attempts tried to convince me something was wrong with my network equipment and tried to sell me their router that doesn't even support my plan. They said I should be getting 40 or more on all channels.