What gives the CMS the right to give out false information?

I have dealings with the csa and now the cms,they say i have a debt of £3974.there taking £630 pcm.which is just under half my wage.i have been ringing them every week for the last 18months.my debt has ranged from £46-£3974,different amount every time i ring.

2014 i was on lo g term sick receiving ssp,the did 2 deduction of earnings leaving me nothing for 2 months running.no explanation why.

2016/2017 they upped my payments for this debt i have paid over £1400 back to them,no explanation where tge debt came from.the rest of this yr saying i still have a debt so agreed to pay an extra £50 pcm till sorted becasue the debt was £1700 after the anual reveiw november 2017.

feb 20l8 payments put up to over £600 pcm,no explanation where debt is from or why so much.i dont eat somedays or have eletric so my daughter can stay at weekends.all they seem to say is when you ring is i cant see all the case but will put a note on the person who is looking into it and they will be in touch in 24hrs….still waiting for 6 call backs 4 from last yr.

i havent seen my 2 youngest kids in 5 yrs due to the mother or knows where she lives but the cms told me 3 times they can send a form to my ex to see if we can swap numbers so i could make contact.complete and utter lies.what gives them the right to give out false info like that.the cms is a joke and run by staff who dont ni what there doing.im ready to give work up and my house as i cant afford to live.getting in debt just to get by.