We have German student staying with us and the school that she is on exchange to requires her to have mobile zone installed on their iPhone to use it in the school. Mobile Zone is not available in the german App store so we can't down load it, we have tried change the region that her iTunes account is set to and we have tried signing out of her iTunes account and signing in with ours to download the app but we still keep getting the same message " that the app is not available for download in the region that the phone is set to. how do we down load the app. could it be that we have not changed the phone language?
You are correct in saying the app is not available from the German store.
Please see this guide with instruction on changing your iTunes region. https://support.apple.com/en-au/HT201389#ios
Once the region has been changed successfully, you should be able to download the app from the app store. Perhaps trying turning the phone off and back on again after the change has been made, to ensure the correct country remains.