To use this function, just swipe from the left screen and bring out the context menu. Or tap the button in top-left corner (). Primary SIM and Secondary SIM will be the command to switch the view from 2 different serving networks. This 2 menu will be greyed out when your phone is with one single SIM inside.

From the pictures, we have 2 SIM in one phone, in the previous version, the views are switching constantly from 1st SIM to 2nd SIM. But from version 1.3, it will be no longer performing like this. The data view of 2 different SIM will show up separately.