Not answering your question (because I don't remember how I got the number associated with DIGITS, but in Android in the DIGITS app I go to advanced options and then Line Permissions, after having logged into the app.

But this is important.

There are two ways of making calls through the DIGITS app - one where it uses the data connection for the call (like VOIP), and the other where it dials a number controlled by T-Mobile and cross-connects you with the number you are calling. Obviously for roaming abroad you want it to use your free data, not to put the call through as a normal roaming cellular call.

If you are in the US and set your phone number to use Data, it will ignore that setting and use the cellular calling network (it will say "this device" next to your phone number.. However, I have found that if I do a fresh install of DIGITS once I am out of the country, it works find and uses the data connection.

You should unconditionally forward your incoming calls so that you don't have the DIGITS app and the phone ringing at the same time. I unconditionally forward my number while roaming to my google Voice number, and either answer the incoming forwarded call using the GV app or let it go to GV voicemail.

Cellular fallback is off by default in the DIGITS app.

I believe you also have to go into your T-Mobile account and enable a line for DIGITS to turn it on in the app.

One final caveat is if T-Mobile knows the line is roaming, even if the call isn't going through the free roaming data, the $0.25/minute may apply, but I have not seen this in practice. I only read it in the fine print T&Cs for using DIGITS, and my data point was from May 2021.

​​​​​​​https://www.reddit.com/r/tmobile/com..._home/jaqc884/

The problem with this approach is not being able to receive calls

Some options: switch to FaceTime (audio) over WiFi

If you have a second SIM and an iPhone (or possibly Android phones can do this too), disable roaming/auto-data switching on the T-Mobile line, it should appear as "T-Mobile Using Cellular Data" and you should be able to make and receive calls over your other SIM card data plan, i.e. equivalent to WiFi Calling (fair warning: this will destroy your battery life)

iPhones XR and newer, Pixel 6, 7 & 8 and Samsung S23 (maybe more) all have the ability to configure a line to use the cellular data of a 2nd SIM for sending and receiving calls. The phones have to be unlocked to add a local data sim.

My son has used a local data sim in Latvia and Rep of Georgia to call us with this configuration without incurring international roaming charges

Our daughter is entertainment crew on a pretty big cruise ship/line. The crew all use Whatsapp for texting and calls since they are in a new country every day or every other day. It also works well on very slow cruise ship wifi or slow cellular data. I am not a Meta fan but we use it for that. We use both Tmo and Google Fi.

That said, they do warn you when you have used some portion of your data. I have the plan that gives me 5GB and got a message when I passed 4GB usage.

With Magenta Max and the new Go5G plans. There’s 5GB of international high speed internet included. Does anyone know if we can tether another device and still get fast internet? Part of the 5GB?

Better than nothing which it almost is!

While using either WiFi calling, or IMS dual sim function, I have always been able to receive incoming calls while roaming.

my ONE plan voice lines with 5Gb high speed data roaming all allow tethering, so I would also expect higher plans to permit tethering. My personal experience is that the tethered devices get approx. 60% of the donor device roaming speed.

I have discovered some useful T-Mobile free roaming features from my current trip others may find useful.

Plans with the 5Gb Canada/Mexico high speed data feature is a separate data bucket from any other on your plan. You should still also have whatever “Free” roaming data your plan includes. So, you get 5Gb HS in Mexico, & another 5Gb for instance in the other 11 or 215+ countries your plan allows without charge. If you have an older plan with the Kickback $10 discount for using less than 2Gb, you will still be allowed the full 5Gb Canada/Mexico HS data, AND the 11 or 215+ country 5Gb HS roaming without losing the $10 Kickback. This is a really sweet deal since it allows the use of spare voice lines with Kickback to utilize an extra 5Gb HS roaming data without penalty.

Additionally, my spare voice lines are receiving free high speed data roaming internationally in my iPads in the countries I have tried them in. So far, several in Europe and also Morocco. I have used them in an iPad Mini 5, Mini 6, and Pro 11”. My ONE plan has the ONE Plus Promo on all lines, and we have 7 lines from various promotions over the years.

Thanks for the info. Glad to hear I can tether off the phone and still get decent speed. I’m actually thinking of tethering an iPad. (No sim, just wifi version)

Without being charged?

Yes, as long as it is between 2 US numbers anywhere your carrier specifies. T-Mobile permits free WiFi calling from the 215+ countries they list. I think since WiFi is a data service it probably also works without charges anywhere WiFi connections are available. I made a 23 minute WiFi call yesterday using cruise ship WiFi and also received several incoming calls without fees, other than the cruise ship package. My wife and I can call each other on the ship over WiFi and they don’t even know. I suppose it would also work in Libya & North Korea, but I probably won’t be testing that any time soon.