That's a great question and thanks for asking potus. With any Non-T-mobile device, it's possible to use features like VoLTE as long as the phone is capable. With that being said, it's not something we can guarantee. You'll wanna take a look at our Bring your own device (BYOD) guide page for more info on using phones you didn't get from T-Mobile. This would go for Wi-Fi as well. For the most part, I've seen more folks have trouble using Wi-Fi on Non-T-Mobile phones.