Chosen Solution
Samsung and At&t can’t solve this problem as my phone will not connect to 4g when I leave my home. It disconnects from home wifi and then will not connect to 4g unless I turn the phone off or airplane mode on and off. My home wifi is the only wifi this happens with as when in another wifi area where phone is connected it has no problem connect back to mobile data or 4g.
Try navigating to Settings > General management > Reset and tap Reset network settings. That will reset your network settings and hopefully solve the problem. Note that this will erase Wi-Fi passwords, and probably Bluetooth devices (not sure, can’t test at the moment).
