One of my clients is a charming young woman who recently started a job in a call centre . I got an urgent e-mail from her.She had started answering the phones and found that when a customer spelled his name for her, she got confused because of the difference in pronunciation of the vowels between Spanish and English. So we got together and I spelled names to her from the phonebook. Every time I said "I", she wrote down "A". This is because the sound we make in English to pronounce "I" would be spelled "AI" in Spanish.
So I just wrote down strings of vowels and read them to her and she wrote them down. After 20 minutes of this she was getting much more accurate. She is going to get her nephew to do this for her at home.