Change WCDMA to GSM automatically I have Samsung Galaxy S II with Android 4.

If I configure my phone to GSM/WCDMA (automatic) mode, I have problems when I receive or make a call. Usually I lost the call or the other person cannot hear me.

In my city 3G network is not very good. 

I solve this problem changing the mode to GSM only (manually) and then make the call.

Is there a way to configure my phone to change from WCDMA to GSM automatically when I make or receive a call? 

I've installed 2G/3G OFF application, but it is still manual.
If you constantly get a poor 3G signal, you may want to switch the signal preference to favor 2G instead of 3G. Here's a way to do it on ICS:


In dialer, press *#*#4636#*#*
Go to 'Phone Information'
Swipe to this 'Set preferred network type'
Assuming it is 'WCDMA preferred', change it to 'GSM Auto (PRL)'



Screenshot (click to enlarge)

This setting will change its signal quality threshold, allowing it to switch from 3G to 2G 'earlier'. Use at your own risk though...

To address your question of automatically switching signal when you make a call, you might be able to hammer something out on Tasker if you are so inclined (I may give it a try later to satisfy my own curiosity xD).

One problem is forsee though, is that I believe it takes a bit of time to switch signals, so it might affect your call (or its quality).