I was irritated with this woman, but said nothing to her during the entire transaction. As she was leaving she announces "Have a great day to you too."
I had something like this happen to me once.
Now, if someone's talking on their cell phone when they come through my register, I usually just keep out of their conversation, only speaking up when I need input from them on something. Sometimes, however -- like in the incident I'm about to relate -- I won't say one word to them. Mostly because I can tell they're the sort who will snap "I'm TALKING, don't interrupt me!" or something like that.
So this woman comes up, yakking on her cell phone the entire time. I just help her unload her cart, ring her up, and when the total comes up, just catch her eye and point to the total. This entire time, she has also NOT SAID ONE WORD TO ME. She's barely even made eye contact. She's much too busy talking to whomever.
She pays me, and about that time, she finishes her call and hangs up. As she hands me the signed credit slip, she then looks at me and says, "You know, you're the rudest cashier I've ever had here? You didn't say one word to me the entire time."
She walks off, while the sheer irony of the situation nearly made my head explode.