How to Flash a T-Mobile to AT&T
If you currently use T-Mobile's wireless service but want to change to AT&T instead, you must prepare your phone to accept a SIM card from AT&T. Sometimes incorrectly referred to as "flashing," this process is more commonly called "unlocking." Flashing is the process of reprogramming a CDMA phone to work with a different CDMA network, such as switching from Verizon to Sprint. The CDMA network doesn't use SIM cards, but the GSM network does. Your phone was programmed to accept only T-Mobile SIM cards before you purchased it, so you must unlock it to use it with AT&T.
Things You'll Need
- AT&T SIM Card
Call AT&T to set up a new wireless account. Tell the customer service representative you plan to use your existing phone.
Dial "*#06#" on your phone's keypad and write down the IMEI number that appears. It's also located under your battery in the battery compartment.
Call T-Mobile customer service to request your phone's unlock code. You must have purchased the phone from T-Mobile and have been a customer for at least 40 days on a post-paid plan or 60 days on a pre-paid plan. If you don't qualify for T-Mobile's unlock code, visit a website that offers unlock codes for a fee, such as Unlock to Talk, GSM Liberty or Global Unlock.
Provide T-Mobile or the online code retailer your IMEI number and phone model number. Both should ask for your email address and online retailers ask for payment information. T-Mobile provides codes for free to eligible customers, and the customer service representative may be able to give you the unlock code over the phone.
Retrieve the unlock code from your email or write it down if T-Mobile provides it over the phone.
Turn off your phone and then remove your battery and SIM card. Place the AT&T SIM card into the slot and then replace the battery and turn on the phone.
Enter your unlock code when prompted on your phone's screen. Call "611" to make sure you reach AT&T customer service instead of T-Mobile customer service.
Tips & Warnings
- Back up any data stored on your SIM card so you can transfer it to the new SIM card after you've unlocked your phone.