Pay for 3 min and get the next 2 hours free for prepay and on Account. Monday to Friday 7pm till 7am (excluding corp and talkzone plans) but does include mobilse, motor mouth, Get plans. All land line numbers in NZ and 021 029.
Please read the T&Cs on the vodafone.co.nz website
http://www.vodafone.co.nz/promos/2hours/2hours.jsp