Telecom have launched a new prepaid add on pack, available for a limited time (Until 31 Oct).
Looks as though as long as you sign up between now and the end of Oct, you can keep the plan as long as you keep your phone topped up enough to let the pack auto renew. If you cancel or do not have enough credit to renew, you won't be able to sign up again after 31 Oct.
This is a fantastic value plan, and exceeds even the XT $40 postpaid smartphone plan in everything but data (500mb vs. 400mb).
Hopefully this is the start of some great value plans to come to the XT network.
http://www.telecom.co.nz/mobile/mobile/plansandpricing/big/