Poor customer service

I was at the shop yesterday. I bought some items in the shop and wanted to pay for the smoothie as I was paying using my card.<br> The teller, I don't know her name as she was not wearing a name tag- till next to the coffee shop, said I can't pay for the smoothie, I asked her why as I normally pay for my fruit salad and just collect.<br> She said smoothie is a new special she doesn't have the code<br> Listen to this- I must go and ask for the code and come back and give her the code.<br> <br> Should I, as a customer go around looking for code?<br> Is it my duty?<br> <br> I emailed the shop at 10:38 and wrote on their Facebook wall. No response no nothing. So it means this is nothing- it doesnt matter!!! <br>