如果你的短信消息包含 Unicode 字符，需要在构造 NexmoMessage 实例时调用 unicode 方法：

/**
 * Get the Nexmo / SMS representation of the notification.
 *
 * @param  mixed  $notifiable
 * @return NexmoMessage
 */
public function toNexmo($notifiable)
{
    return (new NexmoMessage)
                ->content('Your unicode message')
                ->unicode();
}