T-mobile and Cingular are the two national GSM carriers.
Verizon and Sprint/Nextel are the two national CDMA carriers.
GSM carriers (T-mobile and Cingular) have SIM cards. A SIM card has your phone number on it, some times your text messages, and your contacts. If you take your SIM card out of your phone, and put it in a different one, that phone will now ring if you dial your phone number. What ever phone your SIM card is, is what ever phone rings when someone calls you. It will also have you contacts and your text messages.
T-mobile does NOT charge for roaming in the United States. International roaming charges can be found here: Unsupported Browser
Unlocking: Carriers like T-mobile and Cingular do something, called "locking", to their phones. That means that when T-mobile sells a phone to you, it is locked to T-mobile, and you can ONLY use it with at T-mobile SIM card. You cannot use a Cingular SIM card in it, or any other SIM card. You can buy unlocked phones off of E-bay, or, after 90 days, you can call T-mobile and ask them to unlock your phone. They will give you a code to put in your phone, and after that you will be able to put a Cingular SIM card in your phone.
T-mobile does NOT support having two numbers on one phone, or two phones with one number.
I will go over some terms you will probably hear here on the forum:
Deutsch Telekom: The European tele-communications company that owns T-mobile USA.
1900 MHz: The Frequency that T-mobile utilizes for their voice and data. T-mobile uses 1900 MHz, while Cingular uses 850 MHz. Essentially, 1900 MHz is the length of the waves, meaning that 1900 is longer then 850. Due to this, 850 MHz pierces walls and buildings easier then 1900 MHz does. T-mobile has Voice and Data on 1900 frequency as of early 2007
Voice: When you call someone, or they call you, voice is what you hear, and what the person on the other end hears.
MMS: A picture or video message.
Data: The tranfer of data back and forth from your phone. Usually data involves Internet access through WAP or a Java app. Types of data on T-mobile phones listed below:
GPRS: The slowest form of internet on a phone. Usually not over 10 Kb/s (dial up) T-mobile has GPRS almost everywhere they have coverage.
EDGE or EGPRS: A much faster version of GPRS. I get EDGE where I live, and have over 100 Kb/s which is fairly fast. I watch YouTube with 100 Kb/s (its not great, but definitely not bad)
WAP: The kind of Internet your phone uses when it connects to the Internet.
Java App: When you download a game, it uses Java. Java is the coding that is on your phone, that makes games, and other stuff run. Java apps include any kind of game or program you download, weather it be Google maps, Yahoo go, or Windows live.
1700/2100: Recently there was a wireless auction done by the FCC, and they auctioned off the 1700/2100 MHz frequency, and T-mobile's parent company dropped about $4.3 billion to buy spectrum across the United States. T-mobile will be putting 3G on this newly acquired 1700/2100 MHz frequency
