How can I convince my parents?

[Lulu]

My phone annoys me so much. I have a Samsung Focus 2 and when I got it I really expected more of it. It has barely any apps, and the few that it does have doesn't include the apps that I use most: Instagram, Snapchat, and Wanelo. These three apps require internet connection so I can only use them on my iPod Touch when I am at home which is almost never, so I am really mad. I got my current phone last June, and I got it with a 2 year contract. I asked my parents if I could get an iPhone, but every single time I bring it up they never answer my question and change the subject saying they don't want to hear it (mostly my dad, my mom doesn't really say anything, I don't think she knows how she feels about the matter yet). I've made it clear that (since I have my own money) I will pay for the phone AND any fees for changing phones AT&T may charge, but they still have the same response. I am really fed up with my phone, and I don't know how much longer I can take it. What do I do?