CSA fabricate arrears I do not owe

The CSA want £2,319.03 from me even though I am on disability living allowance after sustaining an injury while serving in the army.

When I left the Army after being medically discharged, I’v always paid my child maintenance through my wage packet. When work got to heavy for me and I HAD to go onto D.L.A and incapicity benefit, the CSA sent me a bill stating that I owe £000:00.

I must have got two or three of these letters, then a few years ago, (after the CSA paid themselves £25m in bonuses) they decided that I now owe £2,319.03. they got some debt agency on to me that needed me to send them all my incommings and outgoings, and they came up with some rediculas ammount. Then, that was it for three or four years, now they called me on Wednesday saying I still owe this ammount?????

Do the CSA work in bouts of two or three years?

What is your advice?