iPhone 7 automatically deleting messages

My iPhone 7 has started auto deleting messages. Also I do not get notifications so I never know when I’ve received a message. When sending a text the blue bar never completes so it looks like the message hasn’t sent, although the recipient will have received it. Spent an hour on the phone with Apple Support this morning but they couldn’t solve it. All Settings OK, and texts working OK on my iPad. Can anyone help?