Turning off touch ID has helped somewhat.
When calling my iPhone 7 plus from another there is a long delay before it starts to ring. From my wife's mobile there are often call divert messages coming up which does raise the question again of it being all or partly carrier related.
I am not entirely sure that settings under manual in dnd have no effect when turned off on my phone! It was new yesterday and the whole experience has been extremely unpleasant.
To muddy the waters more my phone number was ported just today! I am going to speak to the carrier (Sky UK)tomorrow to see if the fault may lie with them, their predecessors or Apple or.................
We all know the likelihood of them all blaming each other although to be fair Sky were very good with my initial enquiry earlier today.
Mike.