work your way up the service departments food chain. get the flunkies supervisor out to the house, skip some of the street techs as you could be dealing with someone who has 30 days experience or a burn out with 20 years that lacks the aptitude to do anything else.
or ask for the name of the TOM (Technical Operations Manager) he is the top dog over installs/service.
if you still have a motorola modem (they call them legacy modems here) get it switched out for a docsis type. Ericsson works best here. They use different QAMs (frequencies) and my Ericsson blows away the Motorola in ping tests.
gl