My dad won't let me take my free monthly violin lesson this month as a punishment. Is this fair?

My uncle is my violin teacher, and he's always been willing to give me free violin lessons. He taught me when I was little, and now that I have orchestra at school, I only go to him once a month. Also, my dad is my dance teacher, which he thinks is more important. I forgot to show up one time last week because I was in the middle of practicing the violin, so now he punished me by not letting me go to my lesson. I really need the lesson, though. School is out now for summer, so I don't have orchestra at school, and I'm having a really hard time with some shifting in a solo piece, but my dad won't listen to any of it. He won't even listen to how I like the violin more than dance. I've tried calling my uncle, but he told me to talk to my dad. I've tried talking to my mom, but she told me to talk to my dad. Everyone thinks my dad is the one in control. Is this fair? How can I get him to change his mind?