CSA Overpayment

I was informed whilst serving in the military in Afghanistan in 2001 that I was named as the father and would have to start paying £283 per month.  I found out a few months ago that my son was taken into care in 2003 and therefore was not liable for CSA.

I ‘overpaid’ £24k from 2003 – 2010 I have received this money back plus a small amount of simple interest but the CSA claim not their fault and I am not entitled to be compensated although I had some very difficult periods in my life undergoing debt management and giving up my job in the Army costing me around £250k.  Surely they cannot get away with this.