My first order went as expected. Good price, quick...

My first order went as expected. Good price, quick delivery. Second order placed, forgot to enter discount code. The help tab says what to do, followed the instructions, didn't get empty field to place discount code after order placed. Called customer service, was told they can't add the discount after order is shipped. Not really a huge deal, but why bother giving out a discount code if you can't enter it as directed? Not really happy with them.