cannot sms one contact
Suddenly I cannot SMS one of my contacts from my IPhone 6s. He has a basic mobile phone and up until 4 weeks ago could receive SMS messages from me but now he never receives them. I can receive messages from him. My phone does not tell me that the message has not been delivered. As far as i was aware it had gone successfully.
I have spoken to Apple Support and they could not help.
I have tried the obvious -
Restored phone
Deleted previous conversation
Deleted and re-entered contact details
Manually typed number for message
Nothing has worked. Any ideas??? Help
iPhone 6s, iOS 9.2.1