Got the wrong person!

Today after service class i went to 1U with my service uniform(waitress) to meet up with my mum. We went to the supermarket to get something. I was standing by the side of a cashier counter, while waiting for my mum to pay. Suddenly a uncle called from my back.. He said, excuse me, Miss.. may i ask.... ... MY FIRST WORD TO HIM... SORRY I DONT WORK HERE!!! i was standing at Beer display, it was a promo. for heineken beer.. Do i look like a ''BEER GIRL'' (say in cantonese) ??? my mum was laughing at me.. this was not the first time i get into this kinda of situation. there was one time i was wearing my college uniform with a blue blazer @sinma.. i was waiting for friends while they shop for things at that particular shop and out of a sudden, there's a lady on wheel chair calling me.. i was wondering why.. she said miss can u help me clip this on my hair for me.. i STONE for a moment.. i dont know how can i help her.. i was kind of lost and blur that time.. i was like.. errr... sorry.. i dont work here.. can u imagine those situation? it was kind of embrassing.. i was going for shopping and people misunderstood me as a worker there.. i went to purchase thing and ask for information at certain counter and there's people asking me.. where do u work? u having ur break now?? i told dem i was a student and i just finish my class, the promoter was kinda OPPS... .. i think i should not go out with my uniform specially to shopping centre.. X_x and the worst part is going out for lunch.. people would look at me and my friends in a weird way. In those people eyes i sense the thinking of 'whuts wrongs with those ppl wearing blazer comin to all this place, exp: mamak stall is the worst place to get into..