从隔离的存储文件中添加多个联系人到短信撰写任务

我正试图使SMS撰写任务，从中我可以发送组消息。用户将电话号码添加到一个独立的存储文件中，我打算从那里取出电话号码。

我怎么从那里拿到电话号码?
另外，如何从隔离的存储文件中删除数字?

这是我的隔离存储文件代码:

private void SaveButton_Click(object sender, RoutedEventArgs e)
{
    string fileName = "SOS Contacts.txt";
    using (var isoStorage = IsolatedStorageFile.GetUserStoreForApplication())
    {
        // we need to check to see if the file exists
        if (!isoStorage.FileExists(fileName))
        {
            // file doesn't exist...time to create it.
            isoStorage.CreateFile(fileName);
        }
        // since we are appending to the file, we must use FileMode.Append
        using (var isoStream = new IsolatedStorageFileStream(fileName, FileMode.Append, isoStorage))
        {
            // opens the file and writes to it.
            using (var fileStream = new StreamWriter(isoStream)
            {
                fileStream.WriteLine(PhoneTextBox.Text);
            }
        }
       // you cannot read from a stream that you opened in FileMode.Append.  Therefore, we need
       //   to close the IsolatedStorageFileStream then open it again in a different FileMode.  Since we
       //   we are simply reading the file, we use FileMode.Open
       using (var isoStream = new IsolatedStorageFileStream(fileName, FileMode.Open, isoStorage))
       {
           // opens the file and reads it.
           using (var fileStream = new StreamReader(isoStream))
           {
               ResultTextBox.Text = fileStream.ReadToEnd();
           }
       }
   }
}