Thanks for the suggestions.
The reason for concern is that I expected that at home the iPhone would automatically connect to the Netgear Router, as that wireless network is paid for on a fixed monthly basis with zen - so in effect extra usage is free.
But the Apple iPhone seems to prefer to connect to the EE wireless network.
And that incurs charges.
I expected that to happen only when away from home.
I wonder if Orange/EE preset the Apple iPhones they sell, to have their own wireless network as a preference, to enhance their profits?
On the Apple MacBookPro NETWORK the user can set the preferred method of networking.
Using the iPhone close to the NETGEAR ROUTER does not seem to make any difference.
I am beginning to think that the router is OK - but the error was to buy the iPhone5C from EE [ that was not my decision ].