Customer service told me if there's a data session open when the auto renew happens then the pack won't be applied, instead you end up using casual data, so you should end your data sessions before the auto renew. I pointed out since it renews automatically it's impossible for me to know when it renews, so that's not practical.
They've sent the issue to someone higher up to look into. I can't see txt messages that come through to the device, some weird bug, so I have no idea what the occasional txts I get from 2degrees are, maybe they told me this already.
This is just an FYI for people use use prepay data and data packs to check they get applied rather than assume they work.