One of the first times i paid with my iPhone, the cashier tensed up a little when I authenticated with FaceID before paying. I apologized for being rude by loo

One of the first times i paid with my iPhone, the cashier tensed up a little when I authenticated with FaceID before paying. I apologized for being rude by looking at my phone during the payment, but that I had to authenticate with it with my face to be able to pay. She relaxed and said it was okay, so apparently the unfamiliarity was the source of the confusion.