Sister is leaving NZ for a month in may, telecom launch in june - wants to move to telecom when she gets back, so is it possible to port to them and only have a roaming sim for the month-6 weeks while away, and then change to the new network when she is back?

Shes on vodafone at the moment on an old $20 plan, and they are being stupid about adding traveller and wanting a resign on a term to be able to move (and a more expensive plan)

I can give her a recently freed up cdma phone to port to if needed but it seems crazy if she can just port a couple of days before leaving and then come back and get a shiney new phone then.