network interference and then some

As the title says, I believe that I am dealing with network interference.

My old network name from my old Xfi gateway, Xb7t, is showing up as available. This gateway was replaced, with a brand new XER10 and the network name was changed. I have reset the new router many times, which does not fix anything. Both my old network name, and new network name, remain broadcasted. This issue is across multiple devices. I have freshly installed Windows, and Mac OS, in addition to flushing any cache of saved passwords. 

In total, 18 devices are on my network with only two of those with an RSSI under -51dBm. Most devices have -70dbm. When I initially set up this network, I would be around the -38 to -50 range.

In addition, on my devices page on the Xfinity website, the serial number listed for my "Optical Network Unit" is incorrect. It is actually the mac address of the unit, when it actually does have a serial number. 

Also incorrect, my "Modem-less WiFi device from Xfinity" has its serial number listed as the "Device" MAC address. I have three MAC addresses "Device", "MTA", and "WAN" but no serial number. I have always been told to use the WAN mac address, so this setup seems strange to me.