If it's anything like the mobile broadband hotspot devices that T-Mobile sells, the phone number is not able to make or receive calls but it can send abd receive text messages. I imagine it's not the SIM but how T-Mobile has provisioned the phone number that governs what you're able to do with it.

T-Mobile blocked the voice if you're trying to make voice call on iPhone.

I haven't tried, just curious.

Here is a really silly question that I cannot find an answer to...

If I'm overseas in a Simple Choice country, and if someone from the US texts my US T-Mobile cell phone number, that person does not get charged for making an international text, correct?

That's right. It would be like sending a domestic text message.

Correct, FREE

There is NO way for the network texting to to know you are out of the country, as far as they are concerned it's a domestic text. Now if you were a customer on another network instead of T-Mobile there are charges for YOU to receive a text while roaming internationally. So in theory the only possible would charge would be your network charging to send the text while roaming outside the US however T-Mobile USA does NOT charge for receiving incoming texts when roaming.

Brussels Airport - service was actually pretty fast, 3G.

Japan (Osaka & Tokyo metro areas) - works fairly fast, 3G.

China (Shanghai & Beijing metro areas) - when it works it's so slow, pretty much unusable.

Guam - extremely slow and almost unusable. Also kept getting texts saying I was racking up data charges, but nothing ever appeared on my bill.

China Unicom 3G vs China Mobile 2G
 

Was in multiple cities in China a few weeks ago and phone kept defaulting to China Mobile.

On manual scan for China Unicom it wouldn't fail but would just timeout trying to connect. Then on 5-6th attempt it connected fine and stayed there for the rest of the trip.

Speed/performance was MUCH better than China Mobile.

So to all those who are often in China don't know if China Unicom has issues in timing out SIM authentication to T-Mobile or what but it DOES work but you may need to make multiple attempts to connect to China Unicom (possibly set phone to 3G only)

If someone in the US texts another US number, there's no way they'd get an int'l text charge, whether or not you're in a T-Mobile Simple Choice country, or whether or not you have a Simple Choice rate plan, or whether or not you have T-Mobile or any other carrier on any rate plan for that matter.

I was there recently and used the T-Mobile free data. I attributed the slowness to "island infrastructure" - I also had the signal go from 4-5 bars to nothing repeatedly for no apparent reason.

That happened to me too. T-Mobile confirmed that Guam had been added to the free int'l roaming plan just in March of this year, and apparently whatever mechanism sends out the roaming data usage alerts has not been updated yet. But no roaming charges ever posted to my account.

So the opposite - if I have simple choice and I am in Thailand and text a Thai number is that free also?

Texting is free from Simple Choice countries. (And now also free from the US to almost every country.)

Yes, but keep in mind the return text (Thailand to your US number that happens to be in Thailand) would likely incur a charge to the Thai phone as if they called any US number. No free text for them just because you happen to be there on a free roaming plan.

120 countries + http://www.t-mobile.com/cell-phone-p...50&PID=6147683