unable to create networkmanager proxy using glib

[satya gowtham kudupudi <satyagowtham k gmail com>]

This is c++ code ive written to get Modem capabilities.

DBusGConnection *connection;
    GError * error;
    DBusGProxy *proxy;
    char ** name_list;
    char ** name_list_ptr;
    g_type_init();
    error = NULL;
    connection = dbus_g_bus_get(DBUS_BUS_SESSION, &error);
    if (connection == NULL) {
        g_printerr("Failed to open connection to bus: %s\n", error->message);
        g_error_free(error);
        return false;
    }
    proxy = dbus_g_proxy_new_for_name(connection, "org.freedesktop.NetworkManager", "/org/freedesktop/NetworkManager/Device", "org.freedesktop.NetworkManager.Device.Modem");
    error = NULL;
    if (!dbus_g_proxy_call(proxy, "ModemCapabilities", &error, G_TYPE_INVALID, G_TYPE_STRV, &name_list, G_TYPE_INVALID)) {
        if (error->domain == DBUS_GERROR && error->code == DBUS_GERROR_REMOTE_EXCEPTION) {
            g_printerr("Caught remote method exception %s: %s",
                    dbus_g_error_get_name(error),
                    error->message);
        } else {
            g_printerr("Error: %s\n", error->message);
        }
        g_error_free(error);
        return 0;
    }

Im getting following error:

Error: The name org.freedesktop.NetworkManager was not provided by any .service files

I want to read modem capabilities. Do some one can help me in doing this?

Thank you,

Regards
Gowtham