I got my iPhone 13 Pro Max 1TB Silver, after having my iPhone XS Max 512GB Space Grey for 3 years, not sure what's a good price, it's an at&t model, I see 9to5mac's trade-in site says $350, and then $400 for unlocked, but not sure if 1. I can get the XS Max unlocked, and 2. If I can, would it be considered unlocked? I'm wary of selling on eBay, too many people trying to rip people off, it's basically brand new looking, case since day 1, screen protector, no cracks. Thanks to anyone who has any idea or advice.