To end a call
Simply tap the End button
on the Call screen to end the
call.
If you accessed other device functions while the call was in progress, there are several ways to return to the Call screen to end the call.
Tap the Ongoing call notification (at the top of the screen).
Tap the Home Button
, then tap the Phone icon 
.Drag the Status Bar down, then tap the Current call notification on the Notifications panel.
NOTE
You can also press the Power/Lock button 
to end the
call, if you activated this feature in the Call settings (tap the Menu icon 
in the Phone app).