Empty promises

I got 15% discount to spend at CNA but only to find out that they provide one code to many clients and thus the code doesn’t work. I called them and notified them about this but was treated so bad by both the call centre agent and management who told me that the problem can be resolved after 7 days which won’t help me because I wanted to buy stationery before the school open next week. The problem is how they speak to the customers rather than what they say. We have a long way to go with customer service and integrity in South Africa ???