How to Handle no Santa or Christmas

Is this an appropriate group ? Yesterday we were at a store and my son was upset about not getting a toy, this older woman tried telling him to ask Santa for it and be good for Santa. But we don’t do Santa. My son is 3 next month so he doesn’t know what Santa is but he’s not so young he doesn’t know what people are talking about. It’s so annoying. There are other kids in public so I don’t want to ruin anything for them. We also don’t celebrate Christmas and when we go places everybody asks if he’s ready for Christmas and all this. He doesn’t know what Christmas is. I’m not a person of confrontation so it makes me really uncomfortable to point out we don’t celebrate or believe in Santa. So how would you handle this in the future ? I live in the Bible Belt so you Could imagine someone’s reaction to this if I straight up told them the truth

Edit: thank you for all the kind response!!