incorrect balance

in july i got statement from city of tshwane saying i owe them 5681.00. my bill is normally less than 300.00 every month. on the 21 st July 2015 i took picture of my meter reading, i went to akasia office so that they adjust it for me. on the 7/8/2015 i got another statement sayign i owe them 3530.00. its impossible. i saty in township. i pay less 300.00 everymonth. i asked for time off at work to go there it wasnt sorted and its not first time i got wrong balance amount on my statement.i know my account is uptodate. i dont owe them more than 700.00