Why am I still paying CSA?

Recently phoned CSA to inform them that my son (19 next month) whom I pay £62p/w for into PWC bank account. Said to them my son has been working since July 2014 and not been in education since May 2014 Why am I still paying I asked and all I got was we will be back in touch once we hear from child benefit if PWC is still claiming child benefit but as per usual heard absolutely nothing what a joke they are (money owed to date almost £4000) but highly unlikely I will see a penny of that back (Raging!!!!!!!!)