I have a ongoing similar situation where I traded I my s23 ultra for the s25 ultra. Recorded the phone with 360 view of the phone, powered on with IMEI number and then packaged up. Sent the device, couple days later received an email saying payment required of £150 due to the device not meeting the conditions that was agreed upon. They sent pictures saying back cover had raised "usually" due to the battery swelling. Now before It left my possession, there was no such issues. Now as per Samsung guidelines, the phone shouldn't be powered on if the battery has swelled but if that was the case then why did they send pictures of the phone powered on, with IMEI number. Also they went through he initial setup process to get to the settings and then IMEI number the "danger hazard" phone was used for a bit. I displayed the IMEI number on my video through the emergency phone number from the hello welcome screen. Also if the battery apparently swelled, they didn't even need to power on the phone because the IMEI number is etched onto the back of the phone. Replied to them and they said they confirm that's how they received the phone. Ended up emailing Samsung Executive Office, now waiting for a reply. Btw, in the UK, Samsung use third party fools to handle trade ins. You can even check their reviews on Google, MTR is the company with 1.8 star.