Yes, you can trade in a locked iPhone. However, you'll need to provide the password to unlock it for assessment by T-Mobile or a platform you're using.
Trading in your iPhone can be a great way to get some extra cash or upgrade to a new device. However, before you do so, it's important to prepare your iPhone for trade-in properly. This includes wiping your data, assessing the condition of your iPhone, and understanding the process of your chosen platform. By following the methods and suggestions outlined in this article, you'll be well on your way to getting the best possible trade-in value for your iPhone.