You should downgrade to Radio firmware from 4.4. to 4.3
https://wiki.ubuntu.com/Touch/DualBootInstallation#Getting_phone_calls_to_work_in_Ubuntu_and_Android_4.4
You should downgrade to Radio firmware from 4.4. to 4.3
https:/ /wiki.ubuntu. com/Touch/ DualBootInstall ation#Getting_ phone_calls_ to_work_ in_Ubuntu_ and_Android_ 4.4