You will need to cancel your subscription with Apple or Google first. This will cancel your next payment but allow you to keep viewing Premium content until the end of your billing period. Please see the links below for how to do this for each platform.
Once your digital subscription period has ended you can re-subscribe to a new Print & Digital offering by selecting an offer at subscriptions.nzherald.co.nz
iOS (Apple iPhone or iPad) – Cancel subscription
https://support.apple.com/en-us/HT202039
Android (Samsung, Google or another smart phone/tablet) – Cancel subscription
https://support.google.com/googleplay/answer/7018481