Complaint Review: Joanns Fabrics and Crafts

I was working at this company, in which when I started I was trained on the cash register, One day a customer came to purchase a product, when I rung it up the screen said out of inventory cannot be sold. I called the manager and asked what do I do, and the manager told me to just give it to the customer, so I did. Now ten months later it happened to me again. A customer came to the register and asked me to check the price of a product, when I price-checked it the product came up out of inventory, so the customer said she wanted it so I gave it to her.  Almost a half hour later the manager called the store and said that we were giving stuff away, I said it came up out of inventory, then I asked her how did she know and she said the lady posted it on the internet, so a week later I was terminated and I don't know why I was doing what I was trained to do. I had never had a verbal or written reprimand.