I found a "hacky" way to get cellular data working for apps on T-Mobile with iOS 9.3b2, so I thought I'd share. The first thing you'll want to do is download Unlimited Free VPN by betternet - Best Proxy VPN for Wifi Hotspot Security | Access Sites and Protect Privacy by Betternet Technologies Inc. https://appsto.re/us/q-nB4.i I've tested out a few VPNs for this, but for some reason this is the only one that would work. Next, you'll need to disable LTE and use their 4G network. After that, you'll need to open the app and install their profile. After the profile is installed, you can try starting the VPN in app, but it always fails for me. If it fails, open Settings / VPN. Near the bottom under Personal VPN, make sure Betternet VPN is checked, then tap the toggle under Personal VPN. You'll want to make sure this is on every time you want to use an app that is broken with cellular data for T-Mobile. Let me know if this works for others... Not quite sure why it works for me.