Hi there, my name is David.
You said that you see your display fine, but you can´t ring out, is this ok, right?
I advice in this case you could restart your smartphone, hold down 5 seconds the start button.
If the issue continue then you will need to make a hard reset into your phone.
The hard reset or reset is a proccedure that make your phone like a new phone (software only).
To do this you´ll need to make a backup first, then, connect your phone to iTunes by the cable, and select in the prefferences to make a reset.
If you need more assistance please contact to me by this way.
Please don´t forget to evaluate my answer, it´s very important of us.
Have a good day!
Thank you for your answer. Unfortunately I was in 'panic' mode when I sent it and it was my landline that wouldn't work. I have now seemed to resolve the problem by switching off the router and later switching it back on again.
Ok, the important of all is your phone works fine.