Yes they are offering a trade-in option when you purchase the unlocked Samsung Galaxy Note 9. Trade-in offer details: UP TO$450 trade-in value eligible with trade in of certain phones if you purchase the unlocked Samsung Galaxy Note 9 and if you have the correct phone that meets the trade in requirements. Save UP TO $450 with Eligible Trade-In when you purchase the unlocked Note 9. Best Buy will pay you the $450 on gift card and coupon. NOT ALL PHONES ARE ELIGIBLE FOR TRADE-IN and some of the older phones in good condition will only get you $150 trade-in value. I have put the info below from the Best Buy website and I hope it helps you!
THIS INFORMATION BELOW SHOULD HELP YOU WITH YOUR QUESTION BECAUSE IT IS FROM THE BEST BUY WEBSITE:
UNLOCKED TRADE-IN OFFER:
A return charge will apply on returned unlocked phones. Trade-in offer details: $450 trade-in value eligible with trade in of a Samsung Galaxy Note8, S9 and S9+, S8, S8+ and S8 Active; iPhone X, iPhone 8 and iPhone 8 Plus; Google Pixel 2 XL and Google Pixel 2; LG V30+. Must trade in eligible device and purchase the unlocked Samsung Galaxy Note9. Upon trade in of a valid device, customer will receive a Best Buy gift card and coupon. Valid in store only. Taxes applied to price of phone prior to the gift card credit. Not all phones are eligible for trade-in and trade-in value may vary. Condition, documentation and accessories may affect value. Excludes phones that are cracked or that lack power. Not available in all locations and some stores may have additional limitations. Payment is by Best Buy gift card and coupon. You are responsible for removing any data from your phone before providing the phone for evaluation. You will be required to agree to the terms and conditions. Best Buy reserves the right to refuse any trade-in or to limit quantities for any reason. Not compatible with other trade-in offers. No rainchecks. See a Blue Shirt or bestbuy.com/tradein for details.