I just moved to Germany from New Zealand. When I asked a guy who works at German vodafone if I could actually use German sim card on my NZ phone, he said I can so I'm using it at the moment.
It worked when I texted someone normally but it didn't work when I tried to call *114# to check my balance.
What I should do when I want to call someone and to check how much data I have got left on my phone.
Read more: Can I use German vodafone sim card on my New Zealand iphone?