..maybe I'm over-thinking it but even though it was said and meant with the best intentions I can see why the assistant may have not taken it in the same 'light-hearted' way and may have found it 'sarcastic or condescending' etc...she probably hates having to ask it over and over again herself and knows that customers can find it annoying but still she has to because she could possibly be reprimanded if she didn't/it's part of her job....so as well intentioned the comment was she was probably thinking...'ughhh, I don't need this...AS IF I WANT TO ASK...do I care if you have your card...'....
...anyway, I'm quite blessed with my job because there really are hardly ever 'two days the same' so there is a lot of job satisfaction there but it must be so mind numbing at times to kind of spend your hours/days/weeks doing the same thing over and over and having to ask these same questions...being irritated by having to and kind of knowing your 'irritating' other people by it as well...I just imagine the satisfaction and pleasure of those days when some go home to their families/partners and say...YESSSSSS..!!!!!!!!....SHE/HE BOUGHT THE BATTERIES...!!!!!!!!!!!!!!!!...today was a good day..

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...anyway, I guess it was just one of those things that was meant to bring a smile but maybe a bit of a 'sensitivity' and probably felt like a criticism.....