I work in a metal building. When we had Verizon cell service worked fine. Now we have AT&T and reception *****. Unless you stand next to the 1' by 1' window.
So we added a microcell( range extender), where anyone who needs to use the service must be added , to receive the service. Service works fine now. ( I don't know if you have to pay monthly for the service, or buy the unit outright. ) I think our microcell allows only 10 cell numbers to be added.
Problem is if you're outside the building and walk into the building, the call drops. Same thing happens when you're inside and walk outside, call disconnects.
I wish we had Verizon back.