Takealot not understanding basic math for refund on order.

I recently ordered items from Takealot on order #***. One of the items was cancelled by Takealot from the order though I originally paid R723 for the order with a R150 voucher included. Thus from R873 I discounted the amount for the 5 items. Then when the items arrived without the cancelled item, there was a new invoice indicating the price of the 4 items of R744, minus the R150 voucher to a total of R594. This means of course that I overpaid for the items, and that Takealot owes me R129. However from the customer service responses the indication is the whole time that the voucher covers the item cancelled. This is not true, as I still paid R723, and with the order total of R594 (after the R150 was app****), it would mean that there's a difference of R129, that is owed to me. It's ridiculous that basic math and accounting is not logical in my request, and that what I'm requesting is a refund of the money owed, else Takealot is in fact *****ing R129 from my account!!!