I am confused (and potentially annoyed).  

We now have 2 phones which are on the $19.99 monthly postpay (on account) plan with Spark (as well as Unplan fibre 100).  Been on this phone plan for ever, and the plans usually meet our needs, apart from an occasional shortage of data.  Each plan provides:
500 MB data
100 NZ minutes
Unlimited SMS
-- and no $10 bundle-up bonus anymore

One reason we kept these plans was that overseas roaming was always easier with the plans on account.

I was happy until our daughter stopped this type of plan we had for her, and went on to Spark prepay $19.99, and she gets:
1.25 GB rollover data (capped at 3.5 GB)
200 rollover minutes (capped at 500 minutes)
Unlimited SMS
Data Stack
Half price Spotify (the real reason she changed)
AND occasional extra data bestowed randomly, apparently
AND overseas roaming, while not automatic, is available for purchase.  Not that we'll be doing much of that at present...

I'm getting the impression that Spark wants us to go prepay, and is certainly making it worth our while.  Or maybe they want us to change to Warehouse $16 prepay plan, which is clearly better than our current plan.

What am I missing?  Apart from money.