False advertising

I received an Email stating that I received a fifty rand credit on my account, and the voucher will expire on 1-03-2021. On 01-03-2021 I placed an order, but the credit did not reflect, and the full amount of the order was deducted. On 02-03-2021 I sent an Email to the helpline, enquiring about the credit. After requesting the original Email and the order number, which I supp****, I was told that because I only lodged the dispute on the 2nd, and the credit expired on the 1st, they cannot assist. The credit was not active on my account in the first place, and I placed the order on the day it was supposed to be active.