Nothing but lies from the CSA

I have been paying my child maintenance to the CSA for the last 9yrs(approx)for my 2 children from previous relationship with no major issues other than the usual nights staying over thing etc.

In 2008 my wife and i were blessed with a little baby girl which i dually informed to the CSA as per their orders( relevent child staying with other parent). I blissfully went on paying my allownace to CSA for next 2 yrs as agreed, until a new clacultion fell through door stating the new amounts i was to pay for following periods etc. On checking payments from salary i found to my surprise that i was paying my ex for my wive& i new girl and had been since birth? when i queried this matter i was at first ignored then when pushing further listned too in part? i was eventually told that yes there had been a mistake and that the CSA had taken money from my salary wrongly but was then told in no uncertain terms(bullied) by one of their obviously hard nosed picked for service workers that my money would not be refunded in lump sum as that was not CSA policy? i was told i would have in fact have my payments reduced over a period of least 1 year until their debt to me was over.

I recieved no letter of apology from their seniour management as i had desired and no letters to inform me that all my money had been refunded (hence) still though was in part still being re-paid, then to my amazement on 8/11/12 i had suddenly soemhow managed to have around £3000 ARREARS SINCE 2010 the time i was actually suppoused to be refunded? when i have been quering this matter (over phone) please dont ever do this !

I have had nothing but lies and unhelpful workers stating one thing then doing another. I am currently now sending a letter to relevent people in both CSA deppt and goverment and made copies etc to make sure that i am hopefully listned too? How can this really happen?????? can anyone advise what else i should be doing ,,thnks