Due to changed circumstances, I’m looking at dropping my OneNZ monthly plan to that of Prepay.

However, OneNZ have ceased offering the option to automatically top-up on a specific date, and now only when credit drops to a certain amount.

Looking at other options –

   Invoking a monthly bank payment, but payment could be delayed etc
   Setting up monthly auto-send renewal TXT using phone App
   OneNZ site implies that advance payments would be held in credit, and subsequently used against top-ups (a sort of one-time annual fee)

Any comments or views to avoid remembering the monthly top-hassle welcome.