Paying for 1GB but not even getting half the speed

So, since the instal was completed I’ve never been able to attain speeds over 540mbs. It’s been Fast forward about 7 months and still no change. Decided to purchase the NETGEAR CM1000 modem as well as a few EERO routers and that still did not help. Why can’t this issue be resolved? I contacted Comcast/xfinity tech support and 2 tech visits later and still no better speeds. The next recommended action is to replace my rental equipment and see what happens. Shouldn’t the new modem that I mentioned previously be better or considered a replacement? If this can be escalated to another level on maintenance or engineer status I think it might help with what I have. Can anyone help? Where is my guru?