CSA driving me crazy with their lies

I am presently paying 4 a child that isnt mine an the other kid im paying 4 is in an out of prison an not in further education, iv had long conversations with CSA but getting knowhere, iv requested all paper work on case and i now have this, they say they sent me a letter in 2007 but i told them i was in prison myself an they asked me 2 prove this which i did, it now transpires that they already knew this as it states in paperwork they was in contact with prison staff, also they have got the name wrong of the child on paperwork they sent me so effectively im paying 4 a child that dont even exist and in my eyes if the name is wrong then the whole claim is void and i should be reembursed,they say they offered me DNA test in 2009 when apparently i denied it even though iv had no contact with them untill recently and then it says i apparently admitted it which iv never done, im really hoping that you could possibly help me resolve this as i have mental health problems and this is driving me crazy, thanks !