Great service in grand caymen islands, touchdown at airport, turned on phone waiting to clear immigration and got clear 3G signal.

WiFi calling on verizon 5s with my postpaid TMO card also worked like a charm for free calls stateside!

How did you get wifi calling on your vz 5s?

Part of iOS 8.x upgrade. Should work on all 5s and of course 6 iPhones.

I did encounter one issue last night. Put in airplane mode, turned on hotel wifi and made calls home on phone, skype and line. In all cases, could hear the other party but they could not hear me. When I turned off airplane mode, all was normal.

When I return home, will check my online bill to confirm the wifi calls were FOC. At worse, $.20 per minute :)

I was just in Macau also. No data roaming either though voice calls worked. Luckily my corporate AT&T mobile, which has Unlimited Int'l LTE data, worked just fine.

Cheers,
Kermee

Just wanted to post my experience with this. Did a one month trip this past August to Saigon, the Mekong Delta, Cambodia, Thailand, and Singapore. No service issues and no billing surprises. Service was limited to 3G, although it was good enough. I was using a Samsung Galaxy S4.

Is the 20 cents per minute on calls for all calls?

Calling from overseas location back to the US, calling from overseas location to a local number there?

That's right. I've made use of both situations. The 20¢/minute also works when calling overseas to another 20¢/minute country. (My wife tested this scenario when calling for our airport pickup while transiting in a third country.)

This is correct.

Or what's even neat, if you're lucky, if you have a phone that supports WiFi calling (i.e. iPhone 6) while traveling overseas, calls back the U.S. are free instead of $0.20 USD/min. -- I tested it last month and it worked great at different hotels I stayed at around Asia.

Cheers,
Kermee

Simple Choice supports Wifi calling in the US and looks like data stash to roll over unused LTE?

And tethering is also supported domestically? I know it worked internationally.

Can anyone shed some light on this? I called TMobile about a $15 "LD Roaming" charge that appeared two months in a row and could not understand the gobbledygook answer.

Yes, tethering is supported domestically.

T-Mobile customer services wasn't able to give you any kind of answer? Did you use the phone overseas? If not, is there a way to dispute the item on your bill? You could always take the bill into a store and ask in person.

Gobbledygook, no straight answer. Detailed billing showed 20 cents per minute on all my calls while overseas. If it appears this month, I will try again and hope for a better CS agent on the phone.

Just got back from Grand Caymen and checked on-line to confirm all my stateside calls using TMO on wifi were indeed free!

I had assumed that once we hooked up to wifi and saw T-Mobile in the upper left hand corner of the screen that we were good to go but apparently countries not on the Simple Choice list are excluded.

I mentioned up-thread that we hooked up to wifi calling with data disabled at a resort while visiting the Maldives but I was still billed at $5.99 a minute for over $300 for two calls to Canada, which T-Mobile kindly reversed for me.

I've searched the T-Mobile site again before writing this and can't find any warnings about that - I'm probably missing something. If I had used Skype there would have been no T-Mobile charges.

When you say "data disabled" do you mean you turned on "airplane mode"(which turns off cell phone signals) and then turned on wifi and connected to a wifi network and made a call?