How to convince my mom to let me change cell phones?

My phone is really crappy. All I wanted was a simple phone that could text and surf the Internet. Every five minutes the Internet will crash, it runs out of battery every four hours, and in the week that I've had it, I've butt dialed six people. I asked my mom, and she said that I have to wait! :( How can I convince her to let me switch sooner???