Which button would you click to change a member's tier in a loyalty program?

The choice "Change Tier" is the most appropriate option for altering a member's tier in a loyalty program. This terminology directly conveys the action intended, which is to adjust the tier status of a member. By selecting this option, it clearly indicates that the system will facilitate a change in the member's loyalty level, making it straightforward for users to understand the function of the button.

In the context of user experience and clarity, using action-oriented and concise terminology, like "Change Tier," helps users to quickly identify the correct functions without confusion. Users generally expect a direct designation for tier modifications to enhance usability and streamline their interactions with the platform. The other options might imply related functionalities, but they lack the explicitness of "Change Tier," which is why this choice stands out as the most fitting for the task of changing a member's tier.