How do I convince my mom to buy me a BlackBerry?

My parents are strict, and I just bought a phone 3 months ago, and i want a new one now- a Blackberry. But my mom refuses and she's getting irritated. I want one so bad. All my friends have one! I don't like working so please don't suggest chores, or erins. Please give me tips!! I really wanna go on BBM!!! Please!!!!