AMC Theatres review: Movie tickets

My son is 15 years old he took a friend to the theater on Friday March 6th 2020 at AMC Braintree cinema on Wood Road Braintree Massachusetts. He purchased two tickets online for the way back 650 Showtime. He spent over $33, when you got there they told him he was not old enough to go into the movie. They told him he had to see another movie in the only movie close to that time was a cartoon. Is with a girl and was extremely embarrassed. Call me I went to pick him up he told me what happened.