Final answer:
Michael's behavior has changed to now answering the phone when it rings, influenced by Pam's positive reinforcement.
Step-by-step explanation:
The change in Michael's behavior regarding answering the phone is that he now answers the phone when it rings. This behavior change can be attributed to the positive reinforcement he receives from Pam, who praises him by saying he is the "best boss" when he performs this action.
This is an example of how positive feedback can motivate a person to change their behavior, which could be considered within the realm of basic psychology or social studies, demonstrating interpersonal communication and behavior modification.