Why need to set it as the default phone program and the default SMS program?

This change was made because Google modified the permission usage rules. Applications that do not meet the requirements will be removed from google play. Please refer:https://play.google.com/about/privacy-s … rmissions/
According to this requirement, the non-default phone program cannot access the call log; the non-default SMS program cannot access the SMS record and send the SMS. So you need to set the DW Contacts as the default program to use the corresponding function.

If you look forward to the old working mode. The corresponding apk can be downloaded from here.