Why did I get aprovel for $800 on my iphone and now Im getting charged

I traded in my phone, Mine was in mint condition they approved me for $800 value but now they are charging me full price for a new one? WTF, they also threw in a google watch and said it was free but then added a line for it so Im paying $29 for the line and charged me full price for the watch? WTF so my first bill was over $400, and now Im paying $200 that's $100 more than I paid with CC. They have the stores scaming people left and right and lying to customers to get commission. Do not switch to T mobile

We have a few different types of promotions that we offer and they can get a little confusing. We have some information about how each program works, so if you want to see them in a bit more detail, check out our Support site. Promotional cards, credits, and rebates | T-Mobile Support 

@AVkurt it sounds like they signed you up for a phone promotion and then a watch promotion through the recurring device credits program. I will try to break it down so it makes sense, but I don’t have the ability to see your order or details for your account so you may want to reach out over the phone or through Facebook or Twitter to get exact dollar amounts for your order and account. 

• When you are getting a phone promotion that requires a trade in, you get an immediate credit for the fair market value when the trade-in is processed and then the rest of the promotion amount will be broken up over 24 months to offset the payments for the new phone. For example, you buy an $800 phone, sign up for an $800 promotion, and trade in a device worth $50. You get $50 upfront (usually as a credit towards the taxes or a bill credit). Then the price of the phone and the remaining amount of the credit is broken up of 24 months. 800/24=33.33 and 750/24=31.25. That means that you will see a charge on the bill for the phone of 33.33 and then you will see a credit to match it for 31.25. At the end of the 24 months you will have received $800 in credits total from T-Mobile(Fair market value and monthly credits). Sometimes the credits can take 1-2 bill cycles to show on the bill. If you don’t get the credit on the first bill, you will see two credits on the second bill, so it catches up right away. 
• For the free watch promotion, it sounds like it required the new line to get the free watch. So like the phone promotion, we break up the price of the watch over 24 months and then adjust that amount as long as you continue to meet the eligibility and keep the line. These kinds of promotions really let you maximize what you get for your money because you’re getting a watch line that allows you to stay connected even if you don’t have your phone on you AND a watch without having to pay extra for the device. Those credits can also take the 1-2 bill cycles, but they catch up the following month like the credits for the phones. 

I know it looks like you are paying for the device because you see the charges on the bill, but you should see the credits right along with it. When you complete an order that qualifies for a promotions, you should get a text message automatically that shows that you are enrolled within a couple days of the order. If you didn’t get that message, our experts can double check your eligibility and enrollment if you reach out over the phone or through social media. 

I hope this helps, but if you have questions, I am happy to try to clarify further