How can I convince my mom to switch from AT&T to tMobile?

My Verizon phone kept breaking so we switched to att. that was in February, like, the seventeenth. i have a two year contract with at&t. but i want the tmobile sidekick like, sooooooo much!! dont call me a poser, but i guess i could be considered pretty scene, and sidekicks are important to being scene. if i tell my mom that, shell think im just stupid. what should i doo?