You can go the dialer app through a tap on top of the screen. don't swipe to open the notification. see the video guide from attachment.

Reference Customer Token.

We have noticed we are unable to get back to the current call. When trying to pull or swipe down the notification menu so we can click on the call to end it, we’re unable to do so. 

We have added the Phone app to the allowed application list but that doesn’t allow us to end the call, it just displays the dialer and contact so we can make a new call but that’s it.

We have tried adding android.system.ui to the allowed list so we can swipe down on the status bar but it doesn’t help, the app continues to close it immediately preventing us from opening the call app.