I have some relatives that have come to visit from the UK and they are staying for 4 weeks. We picked up a Spark pre-paid sim for them last night with the basic $19 plan. Everything seems to be working fine except they can't send or receive texts message to/from anyone back in the UK. Or anywhere outside of NZ. Everything inside NZ works fine, we've exchanges message and calls from mine and my wife's phone and they've managed to call the local car hire place.

I've checked all phone setting and can't see any international blocks. Is this something that needs to be enable on the Spark side for a new pre paid connection?