I got my debt letter in October, before all the bad press started and phoned Centrelink. I actually got through relatively quickly and gave my details to a young man who checked their records and eventually advised me that it was the Centrelink system that was at fault - they had misallocated payments or something and the dates they were chasing me for incorrect payment were actually after I had signed off Newstart and started work, so they hadn't even paid me for those dates (one of the days was a Saturday!). He then told me that I had to go online at mygov.gov.au and change the details myself. I asked him if he could just correct it, what with it being their fault and their system, but no, apparently they couldn't possibly fix it, I had to do it myself.
When I went on to MyGov there was nowhere where I could reallocated payments as the Centrelink man had told me, but I found an option to request a review, which I did. A few days later I got a letter saying that I still owed them the $109. I went back online but now there was no mention of the debt at all, nothing.
A few days after that I started getting SMS messages that looked exactly like bad Phishing attempts, so I ignored them. Further SMS and letters arrived from Dun & Bradstreet and I responded to one by telling them about Centrelink admitting responsibility for the error. Unfortunately I also submitted my tax return around this point and soon got notification that the debt had been deducted from my tax return. Cheers Centrelink!
Appallingly!
My debt was only a small amount and I've held off complaining/challenging because I don't want to spend hours on the phone and filling out more forms. But I'm tempted to kick up a fuss now, on principle.