The 3G to 2G TrFo activation is a challenging project which is not yet tested the IoT.. If we can open this feature then the mos should increase apparently. the customer can feel very wonderful voice quality. the call drop rate at the network during hand over is to be dis-creased. 

 But right now one flaw has been seen during implementation, there are two type of silent call occurring in the network

1. Short Silent call: It is due to lake of standard protocol  

2. Long Silent call : It is due to handset...

Huewei should find out the solution ASAP...