paid my centrelink debt, but didnt realise it was already being deducted

C/link overpaid my CCB and i owed them $180, no biggie but slightly annoying at this time of year! i paid it all off in one go, but then i checked online today and the debt is down to $150 because theyre paying it off out of my FTB.
what happens there? i had the option to pay it all so i assume that i'll just get refunded the $30?
would have been nice to have been told it would happen like that, centrelink are usually pretty good like that

:( what a pain in the bum for you! The system will detect that your CCB debt has been overrecovered and they will reissue your $30 - you shouldn't need to do anything but it may take a week or two for the system to detect it and for someone to follow it up. Most likely your repayment hadn't yet been received in the system (can take 48 hours or so if you pay via bpay or post office) when your FTB payment was issued and it has been automatically deducted.