Is my 7 month old boy under age ? To watch a movie

I Planned a family night with my wife and 7 month old son we wanted to watch a movie at the Ridge. We bought tickets for the new Leon Schuster movie. As we are going in the people working at the door stopped us and says my son is underage? The movie states 13PG as I see it a child under the age of 13 must be acompanied by an aduld. It is really sad to say that for the next 13 years I won't go and watch a movie at The Ridge. I feel this is very bad service and I am going to spread the word. Al people with children under the age of 13 must not go to the movies. Worst service I have had in my life!! You will never see me or anybody that knows me again!