[Networking] Scath:
I have spent about a month researching T-Mobile and have developed this guide to help everyone who needs the answers to the same questions I had. Soon this guide will be put into a PDF version that is all snazzy looking and will be updated as much as possible. Please note: I am a father and husband with my own business, so I am busy but ALWAYS mobile, feel free to PM me.

I am trying to list the best phones with the top specs in this thread. If I helped you at all, please thank me.

*** All phones confirmed working on 4G may depend on the coverage for your area.

If you have any changes or things I can add to this please PM me and DO NOT post it here. I will update the thread with credit to you!

Update 06/23/2013

Thanks to an awesome member, ozzmanj1, we have now added the Sony Ericsson Xperia PLAY R800AT to the list of working 3G/4G devices.

Update 03/20/2013

There will be a website dedicated to T-Mobile Network Phones I am building because I love T-Mobile that much :D Customer for almost 10 years now. That is already under development.

There is a new prepaid company using T-Mobile towers, I am in contact with many reps, they are called Solavei. It is an amazing opportunity to get money by referring people to join Solavei.

SOLAVEI - You pay $49/mo for 4GB of Data (no caps), Unlimited Everything Else. - I have used their service and I love it. The incentives to get friends to join and family, and even get paid for it, epic. I have made money and continue to, great setup. You can get to the point where you have no phone bill, PERIOD. I'm almost there xD

MINIMUM SPEC REQUIREMENTS

These are the specs each phone must have to be put on my list

5MP Front Camera or Higher

Front Facing Camera

1GB Ram or Higher

1GHz CPU or Higher

Dual-Core or Higher

4.0" Screen or Higher

250ppi or Higher

BEFORE BUYING

TERMS

GSM // (Global System for Mobile Communications) Also known as 2G, EDGE.

EDGE // EDGE is the new name for GSM 384. The technology was named GSM 384 because of the fact that it provided Data Transmission at a rate of 384 Kbps.

2G // Also known as GSM. Short for second-generation wireless telephone technology. Second generation 2G cellular telecom networks were commercially launched on the GSM standard in Finland by Radiolinja (now part of Elisa Oyj) in 1991.

3G // Short for third Generation, is a term used to represent the 3rd generation of mobile telecommunications technology. Also called Tri-Band 3G.

4G // The fourth generation of mobile phone mobile communications standards. It is a successor of the third generation (3G) standards. A 4G system provides mobile ultra-broadband Internet access, for example to laptops with USB wireless modems, to smartphones, and to other mobile devices.

HSPA // an amalgamation of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), that extends and improves the performance of existing 3rd generation mobile telecommunication networks utilizing the WCDMA protocols. A further improved 3GPP standard, Evolved HSPA (also known as HSPA+), was released late in 2008 with subsequent worldwide adoption beginning in 2010. The newer standard allows bit-rates to reach as high as 168 Mbit/s in the downlink and 22 Mbit/s in the uplink.

NETWORK BANDS & FACTS

T-Mobile offers GSM service in both the 850MHz and 1900MHz frequency bands.

T-Mobile utilizes the 1700MHz, 2100MHz, and 1900MHz frequency band for their 3G data network.

T-Mobile utilizes the 1900MHz frequency band for their entire network. (EDGE, GPRS, VOICE, TXT)

Europe and most of the world use the 900MHz and 1800MHz frequency bands for GSM. For a device to use T-Mobile USA and work in Europe, it would need to support the 1900MHz band and one or both of the 900MHz and 1800MHz bands used in Europe.

CHECK THE BANDS!

EDGE, GPRS, VOICE, SMS/MMS > 2G GSM: 850/900/1800/1900 MHz

3G/HSPA: 850/1700/1900/2100 MHz

AFTER BUYING

CHANGE YOUR APN

Most of the time only International phones will need this step, but you should still check if your 3G is working before this step.

Worldwide APN List for GPRS/DATA > http://xdaforums.com/showthread.php?t=564459

T-Mobile Guide on Changing APN > http://support.t-mobile.com/docs/DOC-1979

Specs are all up to you and what you need!

PHONES THAT SUPPORT T-MOBILE BANDS

PHONES CONFIRMED TO WORK ON T-MOBILE 3G

UNLOCKED

LG Nexus 4 (4G WORKS)

Sony Xperia Ion LT28H

Samsung Galaxy S III T999 (4G WORKS)

Samsung Galaxy Nexus I9250 (4G WORKS)

AT&T HTC One S (For Help CLICK HERE)

AT&T Samsung Galaxy S II Skyrocket i727 (4G SHOULD WORK. VK1 T-Mobile Radio confirmed working by papabear. It can use both i717 and T989 ROMs. Accelerometer is off by 90 degrees for T989 ROMs, here is the FIX) - Confirmed by papabear

AT&T Note i717 (4G SHOULD WORK) - Confirmed by papabear

Sony Ericsson Xperia PLAY R800AT (Up to 7mbps, so far!) - Confirmed by ozzmanj1 - See Device

INTERNATIONAL (Europe, Asia, UK, etc.)

COMING SOON

PHONES CONFIRMED TO WORK ON T-MOBILE 2G/EDGE

UNLOCKED

AT&T Apple iPhone 5 (3G WORKS SOMETIMES)

AT&T Apple iPhone 4/4S (3G WORKS SOMETIMES)

Samsung Galaxy S III I9300 (3G WORKS SOMETIMES) - Confirmed by papabear

All AT&T Phones Should Work (2G/EDGE - Certain Areas 3G/4G)

HTC A9191 Ace, Euro bands (GSM quad band & 3G 900/2100mhz)

INTERNATIONAL (Europe, Asia, UK, etc.)

COMING SOON

UNCONFIRMED PHONES WITH T-MOBILE BANDS

UNLOCKED

Sony Xperia T LT29i

Sony Xperia TX LT30p (Bond Phone)

INTERNATIONAL (Europe, Asia, UK, etc.)

Huawei Honor 2

Huawei Ascend D1 XL U9500E

Huawei Ascend D1

Huawei Ascend D quad XL

Huawei Ascend D quad

Huawei Honor II Quad-Core

Meizu MX Dual-Core

Meizu MX Quad-Core

Xiaomi M1

Xiaomi M2

K-Touch Treasure V8 Tegra 3

K-Touch Hornet II V9 Tegra 3

Send me your working list of phones that are international or unlocked and band specs so I can update this list as frequently as possible.

scathdesolas@gmail.com or PM me on XDA.

SPECIAL THANKS

Jeremy Gruver (Scath)

All Authors and Responders of the Threads I have linked to

Everyone who reads this and is helped by it

DISCLAIMER:

This guide is meant to be a reference and help you decide on a phone to use with T-Mobile's Network ONLY. Any advice posted by others are the opinions of the author of that post and is not official advice from me. I am not responsible for any advice given by others that may be incorrect.