SOS issue when select 3G & 2G

Anybody knows how to fix my BB9900 (bought in China, made by Hungary with unlock version and use here in Phnom Penh, Cambodia ) to detect 3G properly as when I ticked 2G & 3G in network option, it will show SOS immediately, but when I only selected 2G, it will work properly. Currently, no issue with other blackberry phone to connect 3G and even other BB9900 under AT&T, unlock BB9900 which my friend is using still work properly with 3G.

My phone's OS has been upgraded to this latest firmware 9900jAllLang_PBr7.1.0_rel2218_PL5.1.0.571_A7.1.0.7 94_Singapore_Telecom_Mobile_Pte_Ltd and it's original OS from the box iwas also on 7.1 too but all did not work.

I now can not use the phone in 3G & 2G or 3G mode as it's important to have 3G detect cuz of faster data send & receive. It works well for 2G selection.
Or it's a hardware issue in the device? How to check it or recognize whether the phone can & can't support 3G network?

try ringin your carrier to check that your carrier it supporting 3G where you are :)

Go to Options > Device > About Device Versions and see what 3G Bands are on the device.

SwitchBeach is right. It sounds like you have bought the wrong 9900 model for use with your network.
There are 2 different 9900 models, each with different 3G bands. Your friend's AT&T 9900 has 3G bands 1, 2, 5 & 6, whereas yours likely has 3G bands 1, 4 & 8. His works on 3G with your network, and yours doesn't. You will only ever get EDGE at best.
Unfortunately the 3G bands are hardware locked, and there is nothing you can do about this. You can't change them, and installing a different OS won't help either.

Originally Posted by Phill_UK

SwitchBeach is right. It sounds like you have bought the wrong 9900 model for use with your network.
There are 2 different 9900 models, each with different 3G bands. Your friend's AT&T 9900 has 3G bands 1, 2, 5 & 6, whereas yours likely has 3G bands 1, 4 & 8. His works on 3G with your network, and yours doesn't. You will only ever get EDGE at best.
Unfortunately the 3G bands are hardware locked, and there is nothing you can do about this. You can't change them, and installing a different OS won't help either.

But I checked my device and it's BB 9900 with 3G bands 1, 2, 5 & 6. What is the issue? So sad with t
his device...

Originally Posted by veasnamao

But I checked my device and it's BB 9900 with 3G bands 1, 2, 5 & 6. What is the issue? So sad with t
his device...

So you and your friend with the AT&T 9900 are both on the same network?

Originally Posted by Phill_UK

So you and your friend with the AT&T 9900 are both on the same network?

Yes. We have three BB9900 here and two are international version and another one under AT&T. All are the same network.

you can still give a try on installing another os or reinstalling the 794 again