If your phone is the unlocked edition, it supports the T-Mobile
feature. If you don't see the
option in Settings, you may need to enable it while you're on the T-Mobile network.
To do this:
Turn your HTC phone off, and then insert a T-Mobile SIM card to the phone.
See the user guide or how-tos on how to insert the SIM card.
Turn your HTC phone on.
If you see the
SIM card changed prompt, tap
OK to restart your phone.
Note: The prompt may not appear if you've inserted the T-Mobile SIM card when your phone is powering on.
After your phone restarts, connect it to a
From the Home screen, swipe up and then find and tap Settings.
Wi-Fi Calling preference.
and select your
Wi-Fi Calling is not enabled yet, tap its
When you see the
Wi-Fi Calling icon on the status bar, your phone is now ready to place
Wi-Fi calls. Open the
Phone app and you should see the
WI-FI CALL button in the dialer.
Note: Certain T-Mobile SIM cards have similar settings with other carriers. Slide open the notifications panel to check if there's a notification that prompts you to choose a carrier. Tap the notification, and then select
T-Mobile as your carrier to ensure the
Wi-Fi Calling settings will appear.