CSA-Help-What to do when you are overcharged??

Hello :hello:

I'm wondering if anyone can give advice re, CSA.

My OH and his ex have 2 children. She has custody of one and we have custody of the other. My OH pays £280 to his ex per month, we were told we were unable to claim from her because she is in receipt of benefits (tax credits) she is self employed and I'm quite sure that she has more income per person than we do(we are now a family of 4).
Yesterday I calcualted maintenance using the CSA new system and according to this he should be paying £148 and should be able to claim £80 from his ex which sounds much more reasonable and is a huge difference.
I spoke with CSA today and they said his case must remain on the old system until all cases are switched over but no-one can say when this will be. If he does switch to the new system payments will not be refunded if overcharged and the guy I spoke to said that the only way we could have something done about this now would be to lobby a local MP?? Surely not?

Your views would be appreciated....