WiFi calling is decent. I've noticed the quality is more or less the same as the mobile network as long as you have a low latency Internet connection. T-Mobile will give you a signal booster if you have marginal reception inside your home.

Japan, Singapore, and Thailand Part 2
 

Just back from my 2 week vacation. Here's an update since my original post.

Thailand
-After a couple days in Patong the display changed to TH GSM and I had Edge data the rest of my trip. I didn't try to go into settings and force it back on to DTAC. I had slow data service the entire 2 weeks of my stay, and got many SMS messages.

At some point during my trip I applied the 5.0.1 update to Android Lollipop.

Singapore
-On my return trip while spending a few hours at Changi airport, my phone automatically selected and connected to M1. Display was SGP-M1. HSPA+ service.

Japan
-During a layover in Narita airport my phone first automatically selected and connected to NTT Docomo UMTS service but soon switched to Softbank. HSPA service in most areas with some spots where it falls back to UMTS.

It just happened that no one tried calling me during this time, and I made no outgoing voice calls. That's not unusual for me, I use SMS and data almost exclusively. I used WiFi in my hotel, restaurants, and in airport lounges whenever possible. Still I had about 500 MB of cell data usage while internationally roaming in the current billing cycle.

My phone is a Nexus 5 US model running Lollipop 5.0.1 I continue to be very happy with my T-Mobile service.

Question about WiFi calls overseas. Reading the past few pages it seems you get charged calling over wifi, is this correct? If you use Skype when connected to a hotel's wifi to call a non-us number you still pay per minute? I assume this also applied when calling using data when roaming? Are there any voip apps that get around these charges? Not sure how t-mobile knows that certain data is a phone call? Especially when you're connected to wifi.

If you use Skype to call any number you will pay per minute (through Skype, not T-Mobile). If you call overseas using WiFi to a US number there is no additional charge. The problem was coming in when using WiFi to call a third country (Canada) while overseas (the Maldives) the person was billed the cellular roaming rate ($5.99/minute) when he should have been charged as if he had placed the call over the US cellular network since this is how T-Mobile sees the call.

As Lebanon is not part of the plan coverage, just wanted to share the information received once I arrived into Beirut..

Welcome to Lebanon. Out of plan coverage. $.0.50/text and $3.59/min talk.

Caution: Charges for web, email & apps while roaming are $15/mb + tax

Expensive as everything in Beirut...

It will be nice if someone could list them on the wiki

I.e. Skype / Facetime (for mac users) / Viber / Line / Any other app where you can actually call your contacts for free while roaming or over WIFI.

Any of these won't generate charges from T-Mobile when directed over WiFi because T-Mobile doesn't see any of the data. When going over the local mobile network it's governed by if you get unlimited 2G web/data speeds in that country or if it's billed at a metered rate. If the connection is good enough to maintain a Skype/Facetime call, you'll be fine.

The issue comes in with WiFi calling (over T-Mobile's network) to other phone numbers. I have an international discounted calling plan, so I will check out a few corner cases next month.

Got it, so I can use skype and pay their rates when I'm connected to wifi or roaming internationally. Is the "free" international roaming fast enough to place voip calls through skype/google voice normally? If so I'm not sure what the benefit is to use t-mobile's wifi calling or $0.20/min calling? In my experience the cost of skype calls is a fraction of $0.20/min. Haven't really had quality problems with skype if the internet connection is decent.

I got this text from T-Mo today, "Effective January 13, 2015, we are no longer able to offer data roaming in Vietnam (this does not impact voice calls or text messaging). For more details: http://m.t-mo.co/buVvo"

Bummer!

T-Mobile Comes Through! (a bit of Vz bashing...)

The president of our company was traveling to Costa Rica for the holidays, but needed to keep in touch. Our corporate plan is with Verizon, so I went ahead and swapped out his hotspot for an international version and added the data plan (100MB/$25), so that he could keep in touch on his computer. I gave him the 4th line of my "4/$100 plan", which he placed in his old iPhone 5, so that he had 20-cent/minute calls (vs. $2.89/minute on V...). With him in Costa Rica not less than a day, his hotspot stopped working - he texted and I was on the phone with Verizon. Come to find out, they have no roaming partner in Costa Rica, so data is $20/MB - meaning when he hit 50 MB, it triggered the $1000 lockout on the line... I was pissed (as was he). At least his T-Mobile phone was working for data...

Quickly went online to my TMo account and added a 200MB higher-speed plan to my line (for the same $25). I sent him the instructions for turning on "Hotspot Mode" on the iPhone 5, and got the "Worked. Gracias." text message. Whew!

J

My wife used Skype to place a call via the international roaming, and it sustained a conversation for 30 minutes. The benefit of the $0.20/minute calling is if you're not near a WiFi HotSpot and need to get in touch with someone you aren't gouged with a $1-5/minute rate to make a quick phone call. T-Mobile's WiFi calling is free back stateside, but they've changed the billing such that you will have problems if calling anywhere outside of the US in a non-$0.20/minute location. (In these cases, it makes sense to use Skype anyway because the per minute rate is cheaper.)

I just got the iPhone 6 from T-Mobile (2 weeks ago) and went to Mazatlan for the past week. While the texting and phone service was excellent (connected to Movistar) I noticed that even though the phone would indicate 3G speed, there was no data connectivity. I have read that this could be due to the fact that the iPhone 6 does not have support for the signal band that Movistar uses. Has anyone else encountered this, and if so, was there an option on the phone that needed to be changed in order to get it to work?

Most phones should support all 3G bands.

iPhone is suppose to support the most number of LTE bands. The one you buy in the US could be used in Asia and Europe whereas other smart phones have different SKUs for US vs. rest of the world.

Latin America may be further behind. For instance, I was researching going to Argentina, which doesn't have any LTE networks yet.

In the phone, was the option to allow for data roaming, enabled?

But, wouldn't the phone pick up the 3G signal and utilize that, albeit that it would be a much slower connection?

Yes, I even made a point of it to turn it on--when I landed, it acquired the Movistar signal, but for whatever reason not the data part of it. I also reset the network settings too to make sure that there was nothing else in the settings that would prevent it from working.

PS-whatever you do, don't disable iMessage as it is a gargantuan pain to re-enable.