Wrong settlement letter

27 july i was given an amount to pay to settle my identity card,i paid it up all of it ,after 3month i receive a call that i m still owing .I send him proof of payment he said the amount i paid was wrong . I told him that , i paid the amount he gave from his email on the 30 july of july again he said no i was suppose to pay the letter from 29 july but i never receive it . So its so difficult for me because now they want me to pay another money . Wheres i have proof on what i m saying is rite