CSA are doing nothing but encouraging fraudulent behaviour from my ex!

Had nothing but hassle with csa they haven’t helped one bit totally useless my ex gave them false information so he only had to pay flat rate when he should have been paying a hell of a lot more then when I told them about it they did nothing as per usual which is Fraudulent but gets away with it , my ex is now unemployed and pays absolutely nothing csa still to notify me of this was told from my exs mum, it’s absolutely beyond me how csa are getting away with their failures to help parents who are bringing up kids and allowing absent parents to not pay for their responsibilities it’s a joke.