all the information for ofono USSD iface comes from https://github.com/FuriLabs/ofono/blob/trixie/ofono/doc/supplementaryservices-api.txt the introspect for gdbo bindings comes from gdbus introspect -x Signed-off-by: Bardia Moshiri <bardia@furilabs.com> Part-of: <https://gitlab.gnome.org/GNOME/calls/-/merge_requests/742>