Comcast support is useless - Recent Service in the area has impacted (drastically reduced) internet

I live in a large city in a unit of connected townhomes.  I have been getting slow internet speeds over the past month or so (both wired and wireless).   I started to investigate this but until today never did a full investigation.  Each time I restart all my equipment (powercycle) and I have comcast restart my modem via the app.  The internet would start working but my speed was much slower (12 down 2 up) than my 500 Mbps than I pay for each month.  

I was concerned that others were using my secure network slowing my speeds down.  I went to login to my router via the standard internal ip address and I was unable to do so.    I checked the ipconfig via the command prompt and it shows a super odd default gateway (not the one it should for my router) but then has the standard xfinity gateway at the end of 10.0.0.1.  I have all of my own equipment modem and router so I should not be able to see anything via this address but I can.  I can see my neighbors address, thier SSID and all of the devices connected to the network.  Including I believe my own devices.  As a test I powered on my xbox and then powered it off and refreshed the page in between and I can see it show up and go away.  I can also see my PC's hostname on the network.  Via the app it always says it cannot connect to my modem becuse somehow we are connected through my neighbors which is bottlenecking us.

I also checked my internet usage and it shows zero data used.  I have been working from home, my wife and daughter are constantly streaming Netflix (20 hours a day) and I play online games for a few hours each night.  We pay for unlimited data because we are constantly above the 1GB per month.  

I have attempted to call Comcast six times, each time the call connects then they hang up on me so clearly they have no interest in helping thier customers.  The people do not call me back and I have to start the process all over again.  When I call I get a nice little message that they recently did work in my area to "upgrade" my service. 

So what I am pretty sure happened is that when that serivce was done they somehow disconnected my line and we are now all using the same line. This subjects me to a vastly slower plan that my neighbors have.  

Any advice on how to get comcast to remedy this situation would be appreciated.   I cannot seem to get anyone on the phone from comcast.  Should I go to one of their stores?  It is impacting my ability to work as I am unable to use video conferencing with the limited bandwith.  

Thanks in advance for any suggestions.