Can’t call after leaving WiFi calling area

13 Pro Max. When I leave a WiFi calling area, and the phone tries to automatically change back to cell service, most of the time it drops my call. About half of the time, I can’t make a call afterwards until I either reset the phone or switch to airplane mode and then off of airplane mode. I have taken it to the Apple Store, had the phone replaced under warranty, had the carrier check everything, and no changes at all. My dad’s health is getting bad, and I need to be able for him to reach me when needed. I’m at my wits end with this, and can’t find a solution. Can someone please help me?