9.1.3 Switch between app and GSM calls
You can make calls either via the app or the native mobile network (GSM), provided your SIM card is linked to your end device. See also chapter 12 Connection type.
To switch from an app call to a GSM call
You are currently making a call via the app and want to continue it via the mobile network (GSM) - for example, because you are leaving your WLAN environment.
1 Tap .
2 Select GSM call.
*You will now receive an incoming call from the server.
3 Accept the call via End & Accept.
*The app call is automatically ended and the call continues seamlessly via the mobile network (GSM).
 
Please only accept incoming server calls via End & Accept - not via Hold & Accept. This is the only way to end the previous call correctly on the server side. However, this selection only appears if incoming calls are displayed in full screen mode. To do this, activate the Full screen option under Settings | Apps | Phone | Incoming calls.
 
To switch from a GSM call to an app call
You are currently making a call via the mobile network (GSM) and would like to continue it via the app - for example, because you are returning to your WLAN environment.
1 Tap
2 Select App call.
*You will now receive an incoming call from the server.
3 Accept the call via End & Accept.
*The GSM call is automatically ended and the call continues seamlessly via the app.
 
Please only accept incoming server calls via End & Accept - not via Hold & Accept. This is the only way to end the previous call correctly on the server side. However, this selection only appears if incoming calls are displayed in full screen mode. To do this, activate the Full screen option under Settings | Apps | Phone | Incoming calls.