Welcome to Vodafone Community
Just to report after one failed attempt to sync with iTunes, Vodafone did something, after many weeks of asking, and then when it was synced with iTunes with a none-Vodafone sim card in NZ it worked. My wife now has her iPhone 6s working normally. What we didn't get to learn was what exactly was done so that it synced to iTunes. I'm posting this message so others looking at this thread with the same problem will know that there is something that needs to be done by Vodafone to overcome this problem.