We cannot apply a discount to an order that has already gone through, or refund the difference, but we can make you a code to use next time. Just email us at aroo@houndtees.com.au with your order number and ask.
Next time, pop your code in at checkout before you pay. Codes do not stack, so it is one code per order, and they apply to full-priced items rather than things that are already reduced.
If your code would not work when you tried it, see why a discount code might not work.