T-Mobile Network Pass allows you to try T-Mobile's network for up to three months for free, while keeping your existing service with your current carrier. All you need is an unlocked, eligible eSIM-capable phone, and to download the T-Mobile app from the Apple App Store or Google Play store. Then you can experience unlimited high-speed data on the T-Mobile network, all with your own phone, phone number, and apps. A list of eligible phones can be found here.