I really hate customers who speak casually to me

Like, casual talk is actually fine??? For regular customers who are a bit older, I guess I'm like their granddaughter, so when they speak casually while we're just chatting, it's like, 'Hmm, I see~' and I don't think much of it. But when customers speak casually in a commanding tone like: 'Give me that.' 'How much is it?' 'Don't you have anything else?' All I can think is, 'What the heck, do I know you???' Ugh, I can't just sprinkle salt and chase them away...