So try putting your WiFi client device in a window that can see that hot spot's antenna.

A client device can look like a router but has the added feature it picks up the WiFi and puts it onto Ethernet. At that point you cable up to your VOIP and other things. If you want to have your own WiFi you plug in a WAP or "Router as a WAP" (see google.) finds a few. I own an old TP Link TL-WR702N that does this trick as well.