How do you get a cellphone?

I am having an issue with cellphones. I want a cellphone really badly but, my parents won’t let me have one. They say that I am to young to have a cellphone but, i am 13 and everyone in my class has one except for me. That’s a fact. Almost everyone in my class is making fun of me because they say that I’ll be the only freshmen who won’t have a cellphone. I have been begging my parents for a cellphone since the sixth grade but’ they still say no. How can I convince them that I need a cellphone because I am always staying after school with sports and have to borrow my coaches phone and now barely anyone talks to me . How do I convince them.