Refer to this article to understand the process of adding system application to policy.
Following the same procedure add phone and contacts applications.
As mentioned, for this article Huawei Y7/Y9 Pro device is considered, hence applications for the device are being added. For reference, please note package names for phone and contacts applications. Below mentioned package names will be applicable for most of the Android devices (Samsung & LG are exceptions though, as per our analysis)
Phone : com.android.incallui
Contacts : com.android.contacts
Once both applications are added to the policy, click or enable the "Launcher Intent" option for Phone application.
Enter launcher app package name and activity respectively in fields. Here are the launcher intent details for the phone app. Refer above picture
Package name : com.android.contacts
Activity : com.android.contacts.activities.DialtactsActivity
Save the policy by clicking on "Save and Continue"On the device, notice the Phone and Contacts application.
To make a phone call, device users should now be able to search for contacts or dial-in phone numbers from the Phone application directly.