From one figure to another and several different stories. Debt collectors are still taking my money.

September 2015 I received a letter from centrelink stating I had submitted the wrong earnings from Sep 2011 - June 2014. In the letter it stated "You are not being charged a recovery fee for this reporting period". In January 2016 I then received a letter stating "Our records show that the amount owing of your Centrelink debt is $16,310.25. I spoke to centerlink regarding the letter in tears, the first person I spoke to calculated it again himself and stated that he can see a mistake was made and they thought I was working two jobs as my ATO slip said Cambrige clothing however when I reported I said "Joe Black" I mentioned this was actually the same company. He put this is the notes and asked for another recalculation. It then came back that I owed $13,425.92. Various phone calls back and forth and each person I spoke to literally had a different story. Two people said I owed nothing when they did the caculations and others said I owed the money. I was called once by a women from centrelink demanding I pay the full sum, when I tried to talk she spoke rudely and loudly over me saying thats the figure and I need to pay. I asked if I could have the names of the people I had spoken to previously and she said I had no right to ask for that as its private information and she dosent need to tell me. I was in the middle of work in tears. I came home early and called centrelink again - this time another girl spoke to me with a different opinion. I ended up providing full pay slips and appealed the decision. The decision came back that I now owe $12,524.71 - Once again no real explanation was given around how this was calculated and when exactly on what dates I was over paid - so I appealed further. As time went on and the second appeal not finalised I was receiving letters from debt collectors demanding I pay the money immediately- they would send final notices and call on private numbers. They were forceful and aggressive, I recall telling my Mum if I wasn't a strong person I would be suicidal from the stress. They stated if I don't start paying the money back Centrelink could contact my work and choose how much they take out of my wages. I was so stressed and suffered severe anxiety. I was prescribed antidepressents and anxiety medication from my doctor. My final phone calls after the appeal came back again not in my favour was that I knew the way they were caculating it didn't add up. I explained the way they made me report didn't make sense as I was a casual worker and shifts would change constantly. I have always reported, always tried to do the correct thing and I still believe I don't owe the money. I was told they would put in the notes that I wan't a recalculation "however they aren't sure if they will do it and get back to me'. Months later I'm still paying of debt I know I don't know if I really owe and no contact back.