The only caveat here is to do this infrequently. If you have a majority of usage as international roaming for 3 months, T-Mobile may limit your international roaming capabilities.

When I was in Europe recently, I used my iPad tethered to my iPhone with Magenta Max without a problem. The speed was good, and no extra charges.

Wondering about this - my child is going overseas for semester abroad. Will T-mobile cut her off the last month or just throttle more? (She's actually going to be overseas almost exactly 3 months, in three different countries).

The most recent data point that I have is that she would get a warning text after two months of having majority use off network. I don't know if there is an off network use threshold under which T-Mobile wouldn't care, but the consensus on here is to have a majority of on network use each billing cycle if you're going to be taking advantage of the international roaming coverage that T-Mobile offers.

Depending on when the billing cycle ends, it might be possible to have on network use strategically that straddles the billing cycles. She would still likely get the text about excessive off network use, but you could arrange a majority of on network use prior to departure and after returning for a 3-month trip such that you don't have > 2 months off network majority use.

For a trip of that length, I wouldn't risk it, and I would elect to get a local SIM or install an eSIM prior to depature. You can then install the DIGITS app and activate her line in the app. She will be able to call and text using her number within the DIGITS app. The only limitation is that DIGITS cannot receive SMS short codes. If she needs to receive a short code text during the trip, she can always connect to a Wi-Fi network, temporarily enable the T-Mobile SIM and quickly change to airplane mode so that the phone doesn't connect to a roaming partner's network. Be careful, however, since if she gets the welcome text T-Mobile will consider her line to be roaming until she is able to connect to the T-Mobile network again.

If she /he is going for three months tell the child to get a local sim card. She /he can call her /his friends from school without costing a fortune. Tell him/she too download.
WhatsApp. The child can call you for free if you download it also. It will cost around 20 Euros a month for unlimited calls and data depending in what country the child is in.

What happens after the warning text? Cut you off in the middle of the next cycle?

It looks like her travels (which have started) will align almost exactly with billing cycles - 3 months almost exactly overlapping 3 cycles - so when she gets into that third month at the beginning of the third cycle would she be able to ride it out until the end of the third cycle, when she returns home?

We'll see if a SIM may help, though she won't be able to get any US usage in between. It would just be no usage.

I'm not sure what country you said she would be in - but eSIMS are cheap these days for most places. So she could shut off the data from her US SIM after two months and use an eSIM for the last month. Her Whatsapp number would remain the same, which is probably what people will be using in the countries that she is in.

Thanks - yeah, she'll be in South Africa for her last month. So maybe get a data SIM and mainly use that - perhaps she can use a bit of TMobile data if there's some need without getting crosswise.

I haven't seen recent data points, but I remember reading T-Mobile might disable international roaming for some time. If you can ensure that the third month has majority use on the T-Mobile network, I wouldn't worry. Otherwise, I would take a look at getting a local SIM (or eSIM).

Historically, T-Mobile was outright canceling people's service for excessive roaming, but I haven't read any recent reports of that. Regardless, I am extremely careful when I know that I'll be unable to conenct to the T-Mobile network for extended periods.

Another option, assuming you have an eSIM capable phone with you in the US. Transfer your daughter's line to your stateside phone with the eSIM. Run up a bunch of data usage (here is a suggestion: https://testfile.org/), then transfer the line back to your daughter's phone.

Report back on T-Mo experience - never got a warning or any indication the roaming was a problem (at least that I'm aware of - I'm primary account holder). Summary: 3 months, 1 in each country, almost aligning with billing cycle for each switch, no US data usage during three months.

Thanks for the report. My understanding is now T-Mobile will send a text message saying that international data might be deactivated if the line is roaming too much. Absent a text message, I would say that everything is fine.

I'm always mindful of roaming on extended travel since I don't want to be caught up in some policy change. After T-Mobile introduced the feature in late 2013, there were several data points of people whose service was abruptly terminated without warning for excessive roaming. That can represent a huge inconvenience these days with so many places using text message confirmations or one-time passwords. Furthermore, T-Mobile's customer service has deteriorated since John Legere left, and the former Uncarrier has been doing things typical of the other carriers after the Sprint acquisition.

+1
Tho' I would submit it started even before that based on my 20+ years of being with T-Mo (formerly Voicestream).