NOT HAPPY WITH SERVICE

I AM NOT HAPPY WITH THE SERVICE GIVEN I PAID MY ACCOUNT BEFORE DUE DATE MISTAKENLY I USED A WRONG REFERENCE NUMBER FROM MY PREVIOUS LOAN BUT I MANAGED TO SENT THE PROOF OF PAYMENT AS SOON AS I REALIZED THAT BUT THEY STILL HANDED MY ACCOUNT OVER TO THEIR ATTORNEYS EVEN WHEN I SENT THE PROOF TO THE ATTORNEYS THEY STILL KEEP ON CALLING ME EVERYDAY TO REMIND ME THAT MY ACCOUNT IS IN ARREARS WHICH IS NOT I AM NOT HAPPY WITH THE SERVICE.