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.)
https://www.google.com/search?q=amazon+wifi+to+ethernet+client finds a few. I own an old TP Link TL-WR702N that does this trick as well.
I'm going to live in an RV full time while I work and I use a VOIP phone so I will need an Ethernet cable plugged into my phone. My home base RV park has decent internet. They recently placed an antenna at the back of the park close to where I am. However, the signal is weak in the RV.
My question is, can I use a range extender (like Bearextender) in a window of my RV and use a wireless router to grab the Bearextender signal? That way I can use the ethernet cable from the router.
(I don't want to place externally as I don't want to drill a hole in the RV unless I have to)