CMS increases my payments without warning all the time

November 2, 2015

I work full time 40 hours , the child maintenance service want me to £154 a week , I only earn £280 a week my original payment was £74 a week how can they jump my payment by £80 I have had to acquire an i.v.a for my debts as I cannot afford to pay them , each correspondence received from child maintenance service the amount I have to pay increases??? can anyone shed light on this? I am paying for 2 daughters and a son.