I've never traded in a phone before with any provider so I'm not sure 100% sure how it works... I have an iPhone 4s that I bought 11 months ago. I paid for it upfront, so it's fully paid for already and I have accumulated $100 on my tab since then to spend on an upgrade. I've kept my phone in mint condition with cases and screen protectors, so I'm wondering when would be the best time to trade it in and upgrade to the iPhone 5? I'd like to pay for an iPhone 5 upfront as well so I'm just wondering how much extra it would cost me after I traded in and used my tab balance.