When the VoIP service has been configured in the mobile device, the internet call can be set as default call type in the following way.
- go to Menu > Contacts and scroll left or right to the VoIP service submenu (e.g. Provider)
- select Options > Settings
- set Default net call service = Yes (or Default service in certain devices)
After the above change, VoIP internet call will be established when calling from the dial button. The voice calls can still be dialed by selecting Options > Call > Voice call.