Poor customer service

I bought stuff through the express pick up at eastgate only to find out that the size's that I bought were small. Day later I went to the Sandton branch to exchange when I got there I was told by one of the store assistant to take the correct sizes & I can proceed with the exchange. When I get to the till the till operator tell's me a different story that I cannot exchange "online purchase" at the store. They were all in a rush to go home as it was Knock off time I was then offered to be refunded which they did. I cannot wait for 14 days for my money. I am very disgruntled customer. Poor customer service I got from that branch