Even if you have an unlimited minutes plan, turning on Wi-Fi Calling on your iPhone may be a good idea. I find many times that I can get on a Wi-Fi network in places that have poor or zero cellular service, and with Wi-Fi Calling turned on, I can get and receive phone calls. I even walked down the street talking to my wife, transitioning from our home Wi-Fi to Verizon without dropping the call.
Note the Emergency Address verbiage below and read it closely. Unlike cellular service, which knows where you are, Wi-Fi doesn't, so in an emergency make sure to tell whoever you contacted your exact location.