Most annoying in the last two weeks I've noticed that I am not receiving all my text messages. I have switched off iMessage and reset network settings and still no change

Another issue is my exchange emails they only sync when I open the app

Finally my phone states I have to switch on mobile data, but it's already switched on?

I spoke to my provider and data us on at their end

Any ideas how I can fix it

I can send text, but receiving is not happening

Use the following to completely kill imessage https://selfsolve.apple.com/deregister-imessage

Re Exchange what app are you using to access mail? One thing you can try is use the official Outlook app. Make sure notifications are switched on so you're informed when an email is pushed.

I'm using exchange through settings, mail, and setting up exchange. All notifications are on

It's all been fine for about 10 months now it's stopped

Reset all the definitions and update the iOS.