When I am in the US on t-mobile with wifi calling on the carrier name changes to "tmobile wifi" I can make/receive calls no problems, all good. Now I am out of the country (where wifi calling is super useful) and of course since I am oversees the carrier name is whatever carrier I am currently roaming with, even with wifi calling turned on. So how do I know if my calls are using wifi or using regular cell network and therefore being charged? I looked at my bill and indeed I have been getting charges for calls at times I was sure I was on a strong wifi signal with wifi calling enabled. I called tmobile and they were very nice and helpful but basically said its such a new feature for Apple that I need to call them as its probably a bug of some sort with OS8 apparently now they can do automatic hand off between wifi and cell calls as to prevent you from dropping wifi calls if you go out of wifi or loose signal makes sense except there is currently no way (that we could tell) to see if your actually making a wifi vs cell call! Strange thing was that a day or so ago the "tmobile wifi" did appear replacing my current roaming carrier name, but only for a moment. So basically we have a cool new, useful feature, but pretty certain its not really working the way it is intended to - at least when your out of the country trying to make wifi calls.