iPhone 11 Wifi won't work, even after factor reset

My Wifi connection on my iPhone was lagging for a few weeks and would stop and go. Two days ago it suddenly stopped working. I tried to "forget" the wifi network and try again. When that didn't work, I then reset network settings. Finally I did a reboot to the factory settings. Nothing has worked. The Wifi shows that it is connected to a network in settings, but the iPhone still says it is using 4G. I can barely open several apps. I can't go to an apple store because of Covid-19 travel restrictions in the country where I reside. How do I get this fixed?