While I don't want to get caught up in the customer service discussion, I can tell you Comcast monitors signal quality to their modems. As a professional engineer, I can tell you most issues Comcast and other providers experience is poor wiring in the home. Splitters, loose connectors, mis-wired RJ45 connectors, Wi-Fi sharing the same channel as the neighbor's house all cause poor performance. You can check your cable modem/TV status at
XFINITY Status Center - Check for Service Outages In Your Area. FYI, Comcast does not throttle your modem speed. You only need 5Mbps for quality Netflix movies at Mpeg 4 on a large screen TV.