Damaged item returned for replacement which cannot be fulfilled so I am R100 out of pocket due to your applying the discount voucher to my credit

I purchased a shopping trolley together with other items to the value of R1,275.00, I had a voucher of R100 which was app**** to this order. The shopping trolley arrived damaged and I duly returned it for a replacement which they could not fulfill so I request a refund to my credit card. They not only ignored this request and refunded via a credit to my Takealot Account BUT DEDUCTED THE R100 credit OFF THE REFUND - so my purchase of a defective item at R299 that THEY COULDN'T REPLACE is credited for R199 on my account - WHAT A ****** RIPOFF - why not apply the credit to the other items purchased. I can understand if it was something that I didn't want or had purchased in error but to be so UNDERHANDED AND credit the lesser amount is something that will be taken up with the Consumer Protection Department too.