A:AnswerIt would reflect on the Payment plan you have now. They will readjust the bill.
The down payment which is the taxes on the phone is paid when you pick up / buy the phone.
A:AnswerI have Verizon, so all I had to pay was the taxes. Verizon bills me for the phone on my monthly bill. It is is a great phone! The camera is amazing.
A:AnswerNot sure what the price would be but you can always take your phone to the retailer that you have service with and they will give you a trade in price depending on the condition of the phone
A:AnswerI'm very sure they will honor an upgrade, I'm with Verizon and had the option to upgrade a line. I did get a $200 gift card as part of the deal, but this was during the Xmas holiday time.