Bruster's Real Ice Cream

I chaperoned a field trip and brought my younger child who is 4 yrs old. She is also 38" tall, two inches shorter than the max for the free Kids' cone. I ordered an ice cream for me and then a kids' cone for my youngest. The woman who I assume owns the place charged me a dollar for my child's "free" cone. My friend then walked up with her younger daughter who is the exact height as mine and they gave her a free kids' cone. When I asked about the difference the woman said my child was taller than the limit. When I said she wasn't, and in fact she was the same height as my friend's daughter, she said they should have charged my friend the dollar too. I asked why, since they were both under the height, and asked her to come around and look. She said she would credit my card. I told her she didn't have to, I just wanted an explanation on why I was charged. The man, who I believe owns it too, came to the window and said he should have charged my friend and since I'm upset about it, he will