Deliberate Deception

So, my mobile phone has a data pack, which I can't auto refill, I need to manually do it every month, or the data drops to an extortionate rate. I got a text to say my data pack was expiring. I still had $50 or so in credit, I am a casual phone user, so I have opted for a plan where my credit lasts a long time, but I need to pump $10 a month in to data. I did this, I bought a data pack. It said it was successful, on my screen. Next morning, I have 0 credit, because it's all been used up. My data pack was not applied and so just checking my mail automatically, used up $50 overnight. Which is an insane cost, who would actually want to pay that ? Of course, they don't care, I can get some platitudes in broken English if I spend an hour on the phone, but my best course of action is to accept I've been rolled by Telstra again and just suck it up. W Why have a credit that lasts a year for phone, and nothing similar for data ? Why not allow me to set it up to auto refill every month so this never happens ? Because they want to rob me, that's why.