COMCAST service

after intermittent service and one request for a service call I was told they would come but there might be a service charge if the problem was our modem. I bought a new modem and the problem did not go away. I scheduled a service call and they did not arrive in the time scheduled. I rescheduled, the technician arrived about 40 minutes after the end of the time window. He shortened our cable and tighened a few things outside and said it should be better. It is not - I have been on hold for 40 plus minutes trying to get through to a supervisor