Wi-fi calling and microcell towers

Is it true that if I purchase a cellphone  directly from the manufacturer that does NOT have any assigned carrier but IS listed as a compatible device and is sold at a higher price at the AT&T store...is it factual that I will be unable to make calls through Wi-fi when no cell signal is available? I currently am forced to use the At&t microcell tower where i live. It must be attached to the router (att does not even offer internet here) and it must be near a window to be able to keep signal with a satellite ( i believe) to enable a 3G signal for any and all calls. I had to purchase the microcell tower too....(hundreds!) I also have to turn off, and on my phone recently EVERY time I step out of range of the tower to get the phone to reconnect. You are also made to register the microcell tower, and the cellphones that will use the microcell.    Why is this the only way for rural areas to use At&t? When the microcell decides to freeze up, or drops signal...it starts all over again! I had to buy a battery back up unit to power my wifi router when power loss occurs. It was another couple hundreds of dollars, but it can ONLY POWER the router, not the MICROCELL so .....no power, no signal, no phone, no electric or well water pump.....this is because we bought phones at the price we could afford from the manufacturer (buy 1, get 1 free) 2for $150. Can you solve this At&t? Can you put your At&t software in our phones? Can you tell me if i had an Att labled IDENTICAL phone and it was somehow wiped of the operating app that allows wifi calling could it not be reloaded to the phone??? Is it all about locking existing customers into contracts or the next program that raises your bill even higher?? Please explain this issue and the solutions available. Why can i only have 3g service yet pay for lte/4g? Why?