Xfinity/Comcast Wifi is the worst internet I have ever used by far. TERRIBLE WIRELESS INTERNET

This internet is compelte garbage. I have a XB6-T Wi-fi Modem Router xFi CGM4140COM running in a small home, and the wifi wont even span past a 20ft radius. What's even worse, is that I have a RANGEXTD repeater running on the other end of the house to solve this issue. THE ISSUE IS NOT SOLVED. I try streaming twitch at 1080p and it's constantly buffering and is painfully slow. It's unwatchable. I'm paying so much for this internet service and it is compelte bunk. I call customer service, and they're terrible and do not care to help you out. They're hoping that you just don't do anything about it and live with it, continuing to pay the ridiculous monthly payment for the lackluster service. I moved to Boston recently, and started using Verizon FIOS. That internet is incredible compared to comcast. The speeds are fast and the wifi/ethernet connections are reliable. It's half the monthly price compared to comcast too.