due to someone else's mistake I am being charged thousands of dollars that I do not have

I was a full time student, working minimal casual hours for one employer for the entire period when I was a student. For some reason, my previous employer had me on their tax records for 12 months after I had resigned so the Centrelink system sees that as being employed in two different places whilst I was studying. I am now having to go back and recover documents from these employers (which were many years ago and therefore may not have my records anymore) to prove that this system have gotten it wrong. When I was speaking to a Centrelink worker over the phone even he said it clearly looked like an error but I still have to provide evidence of this. So due to someone else's mistake, I am being charged thousands of dollars that I do not have and will have to spend many hours/days/weeks trying to sort this out. I am being made out to be a fraud when I am, and have always been an honest and diligent person in everything I do. I am beyond infuriated which is also making me lose sleep with worry and being overwhelmed by it all.