Coupon given instead of credit due & Promo code which can't be used

First issue: I received a voucher from Capitec Bank for a R100 off on an order over R550. I placed an order for two items - R299 and R280, R579 in total. I also had a R41 credit from a previous payment that I app****. After placing the order and using the voucher code and credit, I paid R438. The supplier didn't have the one item of R280 in stock, so it was cancelled automatically a few days after payment. I was only given R180 credit back. After contacting them, I was sent a R100 coupon code for the difference which is only valid until 11 August and not a credit which would not have expired.

Second issue: There is a R150 coupon code when you buy for more than R550 that they have been sending to my email everyday now since the weekend, which expires tomorrow, 31 August. When I try using it, it says that "this promo code is not valid for this customer account". I wanted to buy an Airfryer which is worth much more than R550.