Balloon payment ****.

I was car finaced by standard bank in 2017 for my Kia Picanto 1.0 street 2017 mode for R150 000, the deal was 60months plus 30% balloon payment, i explained to the sales lady that if do not have the balloon money on my last month what can we do. She told me we can add a year to your contract and on that added year you will be paying for the balloon and i agreed to the deal and signed a 72 months contract in the impression that on the 6th year i will be paying for the balloon money. 30 September 2023 is my final year of the 6 year contract and standard bank is saying i owe them 30% balloon money still, how can this be possible? 6 years plus balloon 30% payment? i have been ****med by standard bank.