Razor Sharp Twit

I walked up to the counter at a fast-food restaurant at the mall. As I was perusing my options, the guy behind the counter said, "can I help you, ma'am?" I responded, "yes, I'd like to get an, um..." He quickly retorted, "ma'am, I'm sorry! We don't serve 'um' here!!" "Ha!" I gasped, purely out of pity and to keep myself from groaning out loud. After placing my order and handing the cashier my money, another customer approached the counter. "How can I help you today, ma'am?" the fast-food artist asked the woman. She replied, "I'd like an, um..." As the words barely escaped her mouth, the employee blurted out, "ma'am, I'm sorry! We don't serve 'um' here!!" I could feel the heat coming off of the cashier beside him. In mere nanoseconds I could sense the poor poor girl's suffering, having to listen this idiot repeat the same phrase, or joke as he probably refers to it, hundreds upon hundreds of times day after day after day. She collected my money as she gingerly fingered a plastic knife in her other hand.