Due to carrier limitations, Touch Voicemail does not work with Wifi Calling enabled. To disable Wifi calling:
When your phone is connected to Wi-Fi and Wi-Fi Calling is available, you'll see "Wi-Fi" after your carrier name in the status bar. If you don't see "Wi-Fi" you have successfully turned it off.
- Wi-Fi Calling is turned off by default.
- To make sure it is off go to Settings > Phone and turn off Wi-Fi Calling.