I tried to apply what you explained in your post on my ngm forward infinity but I did not understand if I had to click on the final menu and select gsm only. Is that correct? I did it trying both wcdma only and then gsm only but when I exit the menu, the phone still was unable to switch 3g from sim 1 to sim 2. I have a THL w100 and it does it in its default stock rom and I find it is a very useful function. What's wrong with your method? Would yu please explain in a different and simpler way and how the results will be?