[{'role': 'USR', 'utterance': 'Good afternoon.'}
 {'role': 'SYS', 'utterance': 'Good afternoon. Can I help you?'}
 {'role': 'USR', 'utterance': "I've got this important letter to send to Hainan. Can I send it by registered mail?"}
 {'role': 'SYS', 'utterance': 'Certainly.'}
 {'role': 'USR', 'utterance': 'How much will I have to pay?'}
 {'role': 'SYS', 'utterance': 'Two yuan, please.'}
 {'role': 'USR', 'utterance': 'Here are the letter and the money.'}
 {'role': 'SYS', 'utterance': 'Wait a moment. It seems that your letter is overweight. Let me weight it.'}
 {'role': 'USR', 'utterance': 'Is it overweight?'}
 {'role': 'SYS', 'utterance': "I'm afraid it is. So you will have to pay two yuan extra. The total charge is four yuan."}
 {'role': 'USR', 'utterance': 'All right. Here is the money.'}
 {'role': 'SYS', 'utterance': 'Here are the stamps and your receipt.'}
 {'role': 'USR', 'utterance': 'What shall I do with the receipt?'}]
{'role': 'SYS', 'utterance': 'You can keep it until the addressee tells you that the letter has been delivered. It is the proof that you sent the letter if it fails to arrive.'}