Complain

I've paid my account on the 2nd of April at the branch but my account is not updated til now and they are busy sending me that my account is in areas. I did send them proof of payment from the branch but still not updated they say I must sent proof of which account the payment went through. How am I going to know which account as I did not make an EFT. I'm not happy with that as my name is listed negative on my credit score