hello, the volte was closed in recent updates. I've come across some of these issues and done some research. the solution is as follows; switch to the test application (CIT) by clicking on Settings / My Device / all features / kernel three times. open the additional tools / modem test tools / MNB configuration installation and activation tool from the menu in the upper-right corner. Change and test the MNB settings as shown in the picture, select and activate the MNB that opens the volte.