If you are experiencing poor cellular reception in a particular area that you are frequently at, please check if the following solutions are available through your network carrier: Wi-Fi calling, signal booster, and cellspot.
While these are temporary solutions, they may be good enough for most people. As a last resort, you could call other mobile carriers to verify their coverage in all the areas you frequently visit, not just the area that is currently problematic. In some cases, they may even let you test drive their network, either with a loaner phone and/or SIM card.
Note: poor cellular reception can lead to the overworking of your phone, as it constantly tries to find and amplify weak signals. This often leads to overheating of the device, as well as the battery draining faster than usual. Therefore, before choosing a cellular network provider, it is best to check their network coverage map to verify proper coverage in the areas that you most frequently access - home, work, travel, etc.