Having buyers remorse. How can I trade my iPhone for another phone if I'm stuck on a contract?

I recently bought the iPhone 6 Plus and I am really having buyers remorse after getting this phone. This is my first iPhone and I absolutely hate it. I wished I would've stuck with android tbh. Its so locked down I can't even do anything. I absolutely regret getting the iPhone. Unfortunately I'm stuck in a contract, sucks for me.

Even tho I'm stuck in a contract, I want to know if I sell my iPhone for cash on craigslist could I simply walk in and just trade it for another phone and keep the same number? How would this work? Would I need the sim card or something? I wanna trade my iPhone for the Galaxy S6 Edge Plus but I'm not sure how all the trading and selling works. How should I go about doing this? T-Mobile told me I have to pay $250 before I can get the Edge for 0 down. I'm broke so I don't have the money, I'm just a college kid. I wanna know would it work if I just sold my iPhone on craigslist for $500 and go in and get the Galaxy S6 Edge Plus for 0 down?

I'd return my iPhone but it's already been 2 months. Honestly its a piece of ****, the headphone jack and speakers are already broken and I haven't even dropped it…

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