Can anyone advise how one goes about disconnecting a Spotify account from a Spark pre-paid plan?

My wife would like to switch phone plans as the $19 Spark one is too low on minutes, and has said she wants to move to Skinny*. While the information's easily available as to how to manage transferring an existing Spotify account to a Spark plan (which we did a while back), I can't find anything to ensure we can preserve our account (read saved music, playlists etc!) when she switches away from Spark.

Thanks for any ideas or advice.

* I realise there's a $29 Spark Spotify plan, and the net cost of moving to this ($10/mth) would be the same as moving to a $16 Skinny plan and she'd have more minutes and data, but she wants carryover minutes and data to provide for fluctuating use and for the pack to include Aus calls/texts, hence the Skinny plan is actually more useful.