By switching to a premium plan ($5 more a month for me) I was guaranteed $500 trade in on my note 9
Not sure about a note 8 but it's def worth inquiring!
Carrier don't normally give a good discount. However, AT&T gave $1000 off for switching and upgrading off with trade-in of any qualify phone listed from their web site. You go where you save money. Don't give in to one carrier.

Seet note below:
You’ll need to:
•Purchase eligible device on a qualifying installment agreement, including taxes on full retail price (up front) and $30 activation/upgrade fee.
•Activate a new line or upgrade an existing line of service on an eligible AT&T unlimited wireless plan (min. $75/mo. before discounts for new customers). AT&T may temporarily slow data speeds if the network is busy.
•Trade-in an eligible Smartphone in good working condition with a minimum trade-in value of $60 within 30 days of activation.
Then you’ll get:
•The Samsung Galaxy Note20 5G for free after up to $1000 in bill credits
•Up to $1000 in bill credits on the Samsung Galaxy Note20 Ultra 5G.
Important notes:
•Credits start within 3 bills after trade-in is completed and will be applied over 30 months. You will receive catch-up credits once bill credits start. Credit will not exceed the lower of the device cost or $1000. Other installment options may be available and credit will be applied in equal amounts over the term of the installment.
•If you cancel wireless service, your credits will end and you’ll owe the balance of up to $1450.
•If you cancel service on any other line on your account within 90 days of activating the line under this offer, device credits will stop.
Qualifying Installment Plan:
•Requires a qualifying 0% APR installment agreement (30-mo. term at up to $48.33/mo.) Other installment options may be available and vary by location. $0 down for well-qualified customers only, or down payment may be required and depends on a variety of factors.
•If buying on the AT&T Installment Plan with Next Up, customer is responsible and will not receive any credits for an additional $5/mo. for the Next Up upgrade feature.
Business customers:
•As long as you have a qualified wireless service agreement for Corporate Responsibility User line of service, you can also buy on an Equipment Installment Plan (24-mo. at up to $60.42/mo. or 36-mo. at up to $40.28/mo.) and credits are applied over term of installment agreement.
•You’ll need a qualified wireless plan (minimum $60/mo. for new AT&T Mobile Share Plus for Business plan before discount), but do not need an unlimited plan. Other qual. plans available. Existing customers can add to eligible current plans.
Eligible Devices:
•Eligible Purchased Smartphones◦Eligible Purchased Smartphones (max Credit $1000): ◦Samsung Galaxy: Note20 5G, Note20 Ultra 5G, (Priced up to $1450)
•Eligible Trade-in Smartphones: ◦Minimum Trade-In value must be $60 after device condition questions have been answered
◦Eligible devices: ◦Apple: iPhone 7, 7 Plus, 8, 8 Plus, X, XR, XS, XS Max, 11, 11 Pro, 11 Pro Max
◦Samsung: Galaxy A50, A8+, Note8, Note 9, Note 10, Note 10+, Galaxy S8, Galaxy S8 Active, Galaxy S8 Duos, Galaxy S8+, Galaxy S9, Galaxy S9+, Galaxy S9+ Duos, Galaxy S10, Galaxy S10 5G, Galaxy S10+, Galaxy S10E
◦Google: Pixel 2, 2XL, 3, 3 XL, 3a, 3a XL
◦LG: G8 ThinQ, V40 ThinQ, V50 ThinQ
◦Motorola: Z4
◦Other: RED Hydrogen One, Razer 2, OnePlus 5
Additional Terms:
•See att.com/unlimited for current unlimited plans. Retired unlimited plans may also qualify (excluding prepaid, session-based, and Data Unlimited at $45/mo. plans). Speed, usage & other restr's apply. For plans available to business customers, see
https://www.business.att.com/categories/mobile-rate-plans.html.
•This is not an early upgrade program. Trade-in device may not be on existing installment plan.
•Trade-in does not relieve obligations under any AT&T installment agreement program or other AT&T Return and Exchange programs including recently-purchased device returns, Warranty, or Extended Warranty. Devices to be returned through these AT&T programs should not be traded in via this credit.
•If trade-in value of device is greater than the credit you are eligible for, you may receive a one-time trade-in credit (value via instant credit or promo card) in lieu of this bill credit. See att.com/tradein for terms.
•To qualify for bill credits, wireless line must be on an installment agreement, and remain active & in good standing for 30 days.
•Installment agreement starts when device is shipped.
•To get all the credits, the discounted device must remain on installment agreement and you must keep eligible service for entire installment term.
•If you upgrade or pay up/off the installment agreement on the discounted device early, your credits may cease.
•You have 14 days to exchange or return the smartphone; a restocking fee of up to $55 may apply.
Pricing, promotions, programming, terms & restrictions subject to change & may be modified or terminated at any time without notice.