I haven't been able to find anything (at least current) that confirms that; if switching from Prepay to Pay Monthly (or vice versa), do you retain any carryover data/minutes?

Looking for something definitive like a link to the explanation/conditions on their website if possible. 

Perhaps @2degreesCare or @SaltyNZ can point me to the right page please?

I am going to phone them up, but trying to avoid holding up phone queues just asking questions by having as much info at hand as I can before calling to make any account changes.

Thanks in advance.
Stu