Nothing but problems since it was purchased. Every few days I find that the phone is off the network. Does not matter if I am on cellular or Wi-Fi. I will try to make a call and get the message Couldn't Connect. I reboot the phone and find that I have missed calls and texts. After reboot it's fine for a few days until it happens again.
Try this, Settings>General management>Reset>Reset network settings. Mind you, this clears all Bluetooth and Wi-Fi connections/settings (in addition to rebooting your mobile network) and you will have to reestablish them.