New T-mobile Sim Cards Fail


Oct 5, 2015
My T-Mobile SIM card broke down and had to be replaced twice in the last three months. There have been other reports, too, that SIM cards from T-mobile tend to fail in Xiaomi devices prematurely, typically after two to eight weeks of use.

This is what I have learned about the problem:

T-mobile SIM cards have a unique function called MEC-Request (Mobile Equipment Change). That function is not implemented in most other providers' SIM cards, but it is part of the GSM specification. When the T-Mobile SIM issues that request, the Xiaomi phone responds with an error.

That's a bug in some Xiaomi phones.

Upon receiving that error, the T-mobile SIM starts running amok. It logs that error condition in its own little flash memory and tries that request again. And again and again, every 30 seconds, day and night. After a few weeks the flash memory in the SIM card can't take any more write requests and fails. The SIM card becomes unusable.

That's a bug in T-Mobile's SIM cards.

The problem was first discovered in conjunction with phones from One Plus, about 2 years ago. Meanwhile, One Plus has developed and distributed a fix.

If you google for the words oneplus T-mobile problem, you will find several reports, for instance, this one:

Now it turns out that Xiaomi phones (or some of them) have the same incompatibility with T-mobile. I know of Kenzo, Kate, and MI5, but there might be more.

What can you do? You have several options:

1. Dump your Xiaomi and get a Samsung, Sony, Huawei, HTC, or any other brand popular in Europe.

2. Get a replacement SIM from T-mobile once every month.

3. Change the provider. If you love the superb t-mobile net coverage, you can go to one of the T-Mobile affiliates, like, for instance, Congstar in Germany.

You may want to wait for Xiaomi to fix the problem, but they might not even be aware of it. Also, they might not care, because they don't market their products where T-mobile operates.

You may want to wait for T-mobile to fix the problem, but they don't care much for exotic phones. Currently, T-mobile insists it's entirely a problem of the affected phone manufacturers, they should fix their phones.

The truth is, there are two bugs. In both the phone and the SIM card. Fixing one of the two would be sufficient to eliminate the problem.
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Confirm for Mi MIX.
After 3 Weeks, Simcard was dead.
Simcard Type C/W7.

Yes, this is not directly a bug of the simcard. Is a bug in the firmware from the phone.
The card asks the phone, can you MEC-Request?
And the phone says yes, instead of no. Then begins the card dead write ...

If Xiaomi does not repair this, only another provider can help, who does not have the MEC-Request in his cards.

Or T-Mobile gives us cards which also do not have the MEC-Request.
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Well, it's certainly a bug of the SIM card. The SIM card executes an excessive number of write operations, ignoring the fact it's self-destructing.

And yes, this happens in response to a bug in the phone.
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I have the same problem. I have changed the sim card 3 times.
I have a Xiaomi Redmi 3S and I live in Austria. My telecom provider is HoT.
Does anybody knows which telecom provider in Austria have sim cards without this MEC feature?

I have the same problem with the Mi8.
2 new SIM cards in 4 weeks.
Is there any work around?