For about 3 years, I had extremely poor coverage with my phone. It didn’t improve much with changing providers. I finally went with a new provider and a new phone. The old one was a TDMA phone. The new one was a CDMA phone. The difference was like night and day. I asked others who lived and worked in the same areas as I did how their service was and what type phone they used. In most cases, the CDMA did better. In your area, the TDMA type might have better coverage. It would depend on what system your provider uses. There IS a difference in cell phones, and knowing it can help.
At a local business location, they had horrible Verizon service. I was also able to identify the cell tower being used (a cellphone app). I called the technical group and spoke with them. I told them that this was a tourist location (over 50 tourists a day), their cell service was spotty at best and that we had no landlines available. I was worried if I had to call 911 from there. I told them the cll tower info and they also (since I was a Verizon customer myself) looked at my cell stats from that location.
I suggested that perhaps they could have one of the antennas on the tower slightly adjusted or perhaps they could install a pole mounted cell unit nearby. They said that they would send us a mini-cell unit. It is a box about the size of a modem or library book. It hooks up to an existing internet connection (we used Spectrum Mobile). It looks to a phone like a nearby cell tower. Your call goes through the Internet connection and is routed to Verizons network just as if you had hit Verizons tower. The unit also has a GPS antenna which you put in the window. That allows the unit to know your location in case you have to call 911. You have to make a slight change to your cellphone to enable the cell to connect to these type of boxes and there is a code you can use to see if you are connected.
For us, because of the type of Verizon service I had, the box was free. and the service was free. If you have to pay for the box, it is about $250. It is worth it to try to get it for free. Our location was somewhat rural and there are no towers above us (cell towers send their signal downward because that is where the people are. They generally avoid sending signals upward towards planes, etc. Oh and here in the tropics, some cell towers loo like a coconut palm tree 
It’s the one on the left.
