SIM I.D. Number

**Trialx** · 05-23-2012, 07:10 AM

I'm sure this has been asked a thousand times, but I can't seem to find the answer. How can I tell the difference between an AT&T SIM and a T-Mobile SIM? I think it's a "letter" in the serial number.
Thanks,
Den

**efparri** · 05-23-2012, 08:47 AM

You are confusing Straight Talk's part number with the actual serial number on the card. All SIM cards have a twenty digit number on them. The first part of the number identifies the carrier.

AT&T Mobility: "8901 410..."
T-Mobile: "8901 260..."
You will notice that the second group of numbers correspond to the Mobile Network Code (MNC) of the carrier: On some SIM card holders, the number may not be broken down into groups of fours. That same number is also on the SIM card itself. If the numbers are difficult to read, a bar code reader app will show the numbers if you have the holder.
http://en.wikipedia.org/wiki/List_of..._United_States
You can use the number on the card to determine to which carrier the basic GSM phones sold by Straight Talk are homed.

**Trialx** · 05-23-2012, 09:11 AM

Originally Posted by efparri

You are confusing Straight Talk's part number with the actual serial number on the card. All SIM cards have a twenty digit number on them. The first part of the number identifies the carrier.

AT&T Mobility: "8901 410..."
T-Mobile: "8901 260..."
You will notice that the second group of numbers correspond to the Mobile Network Code (MNC) of the carrier: On some SIM card holders, the number may not be broken down into groups of fours. That same number is also on the SIM card itself. If the numbers are difficult to read, a bar code reader app will show the numbers if you have the holder.
http://en.wikipedia.org/wiki/List_of..._United_States
You can use the number on the card to determine to which carrier the basic GSM phones sold by Straight Talk are homed.

My SIM will be arriving today, I hope it's AT&T. I just wanted to know who the provider was before I pop it into the phone...T-mobile isn't that great in my area. I'm using a new AT&T unlocked HTC Vivid.
Thanks for clarifying,
Den

**maestroteague** · 05-23-2012, 06:12 PM

Originally Posted by Trialx

My SIM will be arriving today, I hope it's AT&T. I just wanted to know who the provider was before I pop it into the phone...T-mobile isn't that great in my area. I'm using a new AT&T unlocked HTC Vivid.
Thanks for clarifying,
Den

For future reference for anyone who may read this later, this is exactly why we advise people to never choose "unlocked" sim when purchasing their sim. Even if you have an unlocked phone, you should still choose the sim for the provider that you want to be on, the one that has the best service in your area. If it is the wrong one, you would be better off trying to return it and get the other one if tmobile is that bad in your area. Once activated, you certainly can't exchange, but will have to buy another one.

**Trialx** · 05-24-2012, 07:11 AM

Originally Posted by maestroteague

For future reference for anyone who may read this later, this is exactly why we advise people to never choose "unlocked" sim when purchasing their sim. Even if you have an unlocked phone, you should still choose the sim for the provider that you want to be on, the one that has the best service in your area. If it is the wrong one, you would be better off trying to return it and get the other one if tmobile is that bad in your area. Once activated, you certainly can't exchange, but will have to buy another one.

Thanks for all the feedback, my SIM arrived on time and it's AT&T. My data speeds (indoors) have increased as much as 40X...that's not all the time, but I've gone from 50k download (Sprint) to as high as 2200k download on AT&T. I'm not getting all scientific about the test, I'm just running “Speedtest” from the closest tower.
Den