Although this concerns Verizon, it may pertain to other carriers too.
I am often at a location which has very poor Verizon signal coverage. The place gives tours and there can be 25 to 35 or more visitors ot including staff there during the day. Our concern was that people might have to call 911 or want to call other people while there.
Due to the 911 need, I contacted Verizon techs from my cellphone and gave them specific information for the location. They checked my location via GPS and/or which cell tower I was hitting. I know quite a bit about telephone and cellphone service. I asked if they could ‘tweak the cell tower antenna’ or perhaps add a mini cell unit on a pole nearby. Both those cost them money and are not really going to happen. The tech said that what they can do is ship us a ‘network extender’ adapter and that my account qualified for that at no charge. They shipped a device which connects to our cable internet and passes the Verizon calls through it. As you see, this works if we have some type of internet other than the cellphone data service on our cells.
The unit has a GPS antenna in it and thus can report our location on the calls without hitting a cell tower. We went from 1 bar to full bars by using the device.
If you do not get a free device, they do have them which you can pay a monthly fee for.
In any event, it may be something you need to consider if you have sketchy cellphone coverage in a specific location.