I know there are already lots of bad reviews but they're all true. Gazelle advertises one price, then will lowball you once you've already shipped your phone in, hoping that you're too lazy to wait 2 weeks for them to ship it back. It's a scam, and should not be allowed to stay in business.
For reference, I sent in two devices that had been in cases their entire life, no cracks, a few light scratches on the screen but not visible unless you looked for it. They have four grades: Damaged/Broken, Scratched/Scuffed, Lightly Used, and Flawless. They tried to offer me less than the price advertised for the Damaged/Broken grade. The example photo for this tier shows a phone with cracks all over the screen, deep scratches all over the phone, bent, and chipped. The phones I sent in were honestly closest to their Flawless tier example photo, yet they tried to grade both as Damaged/Broken to justify lowballing me. I selected Lightly Used for the first phone, and Scratched/Scuffed for the other, after all they claimed they would increase the offer if it was in better condition than stated. They dropped the offer $150 each from the advertised price. I didn't really care about the money at that point, but I declined on principle because I don't want to support a scam site. I'd actually get a higher price at those vending machines at the mall lol.
I doubt any of the other "mail your phone in" companies are any better, I would steer clear of them and do the transactions in-person or through swappa. Thankfully this is the last time I'll have to deal with this process since I went with Apple's upgrade program this time around.
Sorry to hear you’ve had a bad experience. Have made several purchases from gazelle and a few trade ins, never had an issue.