You need two things..
- The SIM that came with your Galaxy S II. If you didn't use that when you got your phone, WiFi calling won't work.
- You need the latest firmware to be installed on your phone. This can be checked for by installing the Samsung Kies application on your computer, and following the prompts. http://www.samsung.com/us/kies
From the home screen hit the menu button and go to settings > wireless and networks > make sure that wifi calling is checked - that will turn on wifi calling. There is no dedicated wifi calling app on the Samsung Galaxy S II.
Then, go into wifi calling settings and you can choose how you want the phone to connect - always use the wifi connection when available or only use the wifi connection when no cell signal is available (that's how I have it). You'll know wifi calling is active because there will be a blue square wifi icon in the left side of your notification bar at the top of your phone.
Hope that helps along with all the helpful information clevernickname provided!
Thank you very much for your help. That is exactly what I was doing, but according to T-Mobile, I did not have WiFi calling on my plan or it wasn't activated. It seemed like it wasn't working correctly, and more importantly, the 4 bars were on when I was calling. I was just trying to make sure I was not being charged roaming while calling from Canada. This is a very imprtant feature for me, as I travel out of the country a lot, and international packages are expensive, and this WiFi calling helps out greatly.
I am trying to give T-Mobile and the Galaxy S II a fair shake, but a lot of drop outs and everyone I call, says there is an echo and it is hard to talk. The echo is them hearing themselves.
Once again, thank you for your help. Wish the store employees were this helpful.