Their iPhone displays 'Telecom NZ' when when on Vodafone.
What has happen is you have put a XT Sim card in your iPhone and when you put your Vodafone sim back in it seems to think that your still on Telecom, when your really not.
How to fix:
- Turn your iPhone off
- Put the XT Sim card in the iPhone
- Turn on iPhone
- Go in to Settings --> Carrier
- And select 'vodafone NZ'
- Turn off iPhone
- Put Vodafone sim card in iPhone
- Turn on
I hope this helps as a guide. YOU DO NOT NEED TO RESTORE YOUR iPHONE DESPITE WHAT VODAFONE TELLS YOU!