In Altru, you cannot upgrade or downgrade between different membership programs. You can only upgrade or downgrade between membership levels in the same membership program.

If a member wants to move to a different level in a different membership program, you can:
  1. Cancel the current membership and sell them a new membership in the other membership program
    1. To cancel a membership, go to the Constituent record for the member.
    2. On the Membership tab, click on the Other Tasks gear icon.
    3. User-added image
    4. Click on the Cancel Membership option.
    5. User-added image
    6. In the Cancellation Reason window, choose the appropriate reason. If you need to add a reason, click on the Spark Notes icon.
    7. User-added image
    8. Click Save
Or
 
2. Sell them a new membership in the other membership program and let the current membership expire

For more information on selling a membership in Altru, please see the following Knowledgebase:
How to sell memberships in front and back office