Intermittent cellular connection loss on iPhone 11 Pro Max with iOS 18.2.1

My iPhone 11 Pro Max keeps losing connection to cellular, and each time it happens, I am unable to make or receive calls or receive texts from non-iPhones. I know the area I'm in has poor coverage (I'm on Cox), but I had never had this issue until a few months. If I shut down the phone and turn it back on, or go in and out of airplane mode, it will reconnect but then loses it again within hours or sometimes minutes. It's running iOS 18.2.1 if that's helpful information. I'm missing calls and texts and use this device for my job and need a solution that lasts longer than a couple hours. Thanks for any help!

[Re-Titled by Moderator]