I am so glad I read these forums before I traded in my S10+ for a S21 Ultra! I received an email from Samsung this morning stating that I had agreed to trade in an S10+, but the phone Samsung received was not an S10+, and they were going to charge me $200 towards my trade in. I called Samsung support, and the woman asked if there was a picture in the email of my trade-in. I told her no, and she asked me to send her a picture or video of my trade in. Luckily, I listened to people on here, and I recorded a video of myself packing my S10+ to send to Samsung. When I emailed her this, I received a return email from Samsung stating that I would not be charged the $200 since they did not prove I had sent the wrong phone. Always have proof of the phone that you’re trading in before you mail it!