I went to Wawa the other day and bought some drinks, pretzels, sandwich and gas. The kid (15-16 years old) rung me up, silently, and then pointed to the credit card machine (Never told me the total, either. He just pointed). I was flustered because I thought maybe he was a mute (seriously), and handed him my card instead of using the card machine..
I guess he screwed up and charged my card for only the drinks and food and the gas was left unpaid. He stood there confused for a minute and called over the manager who was a few feet away. She told him what he did wrong and the kid got all defiant and was saying "NO, I didn't!" The manager was getting frustrated with him (on top of him being rude to her, she had to fix his screw-up at the same time). I was just standing there silently. The manager fixed everything by refunding my card and then had him ring it all up again and charge it for the right amount. Again, he was silent and, again, pointed to the card machine.
I thought the kid maybe had a psych. problem or just didn't know how to treat customers. He didn't say a word to me (or any customer for that matter) the WHOLE time I was there. He never said "Good afternoon," "Your total is $__," or "Sorry I messed up. I'm new" or something. Since he spoke to the manager I know it's not a physical problem. However, the manager seemed upset with him, too.