I was wondering if you knew anyhting about unlocked phones like these: http://www.koobay.com/ms?rt=detail&pid=25374
I'm really hesitant to buy a knock off, but I was mostly wondering about the bands:
GSM 850/900/1800/1900MHz for worldwide use
3G WCDMA 850/2100MHz
Would that only run the EDGE? And have the 3g, 1900MHz upgrades come to Los Angeles yet?
It seems nothing to do with bands but your phone setting, follow the following steps:
1. Go to 'settings'
2. 'More settings'
3. 'Mobile networks'
4. 'Network operators'
5. 'Default setup'
6. Select 'manual'
7. Finally select 'T-mobile'.
You are done and ready to use 4G data on SS S3.
The issue persisted because the default settings for network selection is 'auto' and at&t operator is initially set therefore your phone always select at&t as first choice that's why you can not get 4g signal.
This is only true if you are in one of the areas where T-Mobile has already refarmed to the 1900MHz frequency. Elsewhere, the phone will be limited to painfully slow EDGE data as the band utilized by T-Mobile for 3G/4G data is not supported on the AT&T Galaxy SIII - regardless of whether it has been unlocked or not. Finding all this out the hard way as I made the switch and have only EDGE at home and around my local area. Drive to the 'city' (which has been refarmed) and get full LTE. If you're curious, you can learn more about this and read about my fiasco at www.tmobile-lies.com.