Single Mum sent 2 debts

I am a single mum who works part-time.
I first received the threatening letter everybody did on 13 October 2016 from 'Task force Integrity', scared my details were not up to date I logged on a daily checked, all was fine. I changed no details and just clicked save.
This apparently deleted my eligibility for rental assistance and the Family Tax Benefit, so I received an 'amount payable approx $3000'.
I paid the debt and asked why my rental assistance had stopped. Centrelink said i had to provide my lease and a application for rent assistance despite not having moved.
I sent in my application again and appealed the debt. I was told I didn't owe any money and in fact they had under paid me approx $950, which they paid me, but it took them 6 weeks to repay my $3000.
Then on 9 Feb 2017 I got a second 'account payable' debt letter staying I had to pay them back the $950 they had just paid me as I was over paid.
I called to organise an appeal and had to organise a repayment plan even though my case was being assessed. I offered to pay back $20 a fortnight which was accepted. I was then called back by centrelink saying I had 7 days to repay the $950 as they could see I had that amount in my savings account and so had to pay in full.
I said my money was in a term deposit and they told me, that it didn't matter - I had to pay in full and break my term deposit even though my appeal was under assessment and if I didn't they would pursue legal action against me. They they tried to get me to pay the debt back by giving me bday details over the phone. I insisted that they send me a letter.
The same day I was called and told that my debt had been assessed and i did not owe any money. They sent me a letter confirming I do not owe Centrelink any money.
The stress and upset has affected me so much I have been scared and depressed.
I am constantly trying to get a full time job to support my 4 year old son, to earn enough so I don't have to live in fear of Centrelink. I am expecting I will receive many fake debt letters from Centrelink... but the way the staff treat you on the phone and in person is deplorable.
The fact you have to make repayments even though your debt is being reassessed is criminal.
The fact they expect you to pay them instantly but hold your repayment for 6 weeks is unacceptable.
The treatment of single parents to leave their children in childcare 5 days a week for 10 hours to earn an income just so Centrelink doesn't harass them is despicable.
We are vulnerable. We are alone. We are being attacked. Shame on the government.