How to convince a stubborn person?

My mom put my old phone in the washing machine so i need a new phone my old phone was the pantech laser (it sucks) I asked my mom about getting an iPhone and she is completely okay with it as long as my dad said yes.yesterday i wrote a very persuasive essay and worked really hard on a whole power point. I gave him the essay to read and i was very calm and nice about it but he refused to read it. So i asked him why he didn't want me to have an iPhone and he said because there's 24/7 access to the internet and he says my grades will slip. Right now i have an iPod touch and i'm a straight A student and i don't let the iPod (which has internet) distract me.money is not the reason he doesn't want me to have one. He is just really controlling. I used to play soccer for this one club that costed A LOT of money but i went to another club that's a lot cheaper, also i have been asking for fewer items. I don't know what else to do! Can you please help me i really want one and i don't know how to get it into his brain that i'm responsible and can handle one.

Assuming he knows your Ipod has internet capabilities, I think waiting maybe 2-4 days would determine whether he'll give in or not. Other than that, as a stubborn person myself, I'm not really sure. Stubborn is stubborn, surely your mum could convince him. Maybe say you'll study downstairs or show proof of study.