Easy things first with no guarantees.....On the telco router you are using in the shop you say you are using "router port". Do you mean a LAN port? You should NOT be using the WAN port as this would create a double NAT scenario. You should only be using the LAN ports. You should also make sure the Router has an IP address assigned to it that is on your local network turn off DHCP in that router.
If you configured your Nanos "normally" they should not be doing any traffic shaping or manipulating that would impact wifi calling. | 
wifi calling not working on ubiquiti bridge.
