Message sender's name not appearing on lock screen
Since a few months ago, a contact's name stopped appearing on the lock screen of my iPhone 4s (iOS 9.1) when I received a message from them - just their phone number. Additionally, by necessity, they have their own message tone and ringtone but the default ringtone is played instead.
As I mentioned, this worked perfectly well for at least two years. I have tried resetting the network settings, restored from backup, deleted contact and saved it again from the dialogue in a received message but it simply refuses to show their name or play their personalised tones.
It is probably significant that they do not have an iPhone and that their messages are coming via SMS but I can't see any settings which may account for the odd behaviour. But it is quite important for reasons of priority that they at least have an individual text tone.
I would be extremely grateful for any advice.
iPhone 4S, iOS 9.1, 32GB