Getting 400mbps download, but switched to and paying for 1.1gbps internet service. 4 hours of live agent chat to no avail!

We recently switched to 1.1gbps internet from our previous plan of 600mbps.  We received and activated the Xfinity xFi gateway (XB8) and are only getting around 400mbps which is about what we got with our previous plan and 8 year old modem.  They reprovisioned the gateway, corrected how it was listed in billing and updated the firmware and after still not solving the low speed issue, sent a 2nd xFi gateway to activate and still had the same low speed. 

In the account on the website, it states our plan is 1.1gbps which is what we are paying for.  In the Xfinity app, it shows the gateway getting 1.25gbps. 

However, also in the Xfinity app for our internet service, it states 600mbps as our plan. 
When doing Xfinity speed test, it also states 600mbps as our plan.

After 4 hours of live chat total with various agents, the last agent said the downstream power level was out of spec at -14 dBmV and that was certainly the issue causing the low internet speed.  He supposedly booked a technician to come out the next day to fix the issue (assuming at the street box), but nobody showed up.

With the Xfinity app showing gateway getting 1.25gbps, not sure how the downstream power level can be the issue, but also concerning is that in 2 separate places on the Xfinity app, it is stating our internet service is still 600mbps.