The correct spelling of the phrase "am duty to" is "I am due to." This phrase is often used to indicate that someone is expected or scheduled to do something at a certain time. The "due" in this phrase is pronounced as /djuː/, with a d sound followed by a yoo sound, while the "to" is pronounced as /tuː/, with a t sound followed by an ooh sound. It is important to use the correct spelling and pronunciation of words to ensure clear communication.