Hi cordelia921!
The trade-in program is very handy, if you want to make some money for a device you are no longer using. The promo code box is there if the trade is qualified for a promotion. If you do qualify, you would have been provided with the code. Please check the paperwork for a promo code. If one isn't listed, then you did not qualify for the promo.
Hope this helps!
Christina B
VZW Support
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