iPhone 12 Pro Max antennae issues

My wife and I appreciate your situation. We also bought new iPhone 12 and now face the same situation. And, solutions suggested by Apple and Verizon, have not worked. We have very limited cell reception in our area. We purchased a cell signal enhancer that worked well on previous iPhones (6+ and 10). When we place different model iPhones next to each other, all with the same settings, only the iPhone 12 does not receive adequate signal (it does not state "no service" simply no bars and no calls or texts). I think besides poor coverage in our area, the new 5G antenna on the iPhone 12 does not pick up 3G, 4G or LTE as well as older models. Either that, or something else in the hardware interferes. As mentioned, we've tried many well-meaning suggestions to no avail. Please post any changes to your situation that results in improved reception. Thanks.