Hopefully I'm understanding you correct. I think this link will help you : http://www.paidmembershipspro.com/documentation/membership-levels/upgrade-or-downgrade-a-users-membership-level/
NOTE: you will need to register a free account so read the full details, but as it reads from Jason site (he is the creator of PMP )
Upgrade or Downgrade a User’s Membership Level
The site administrator can manually update a user’s membership level through the WordPress admin or the member can change their own level through your site.
For the Site Administrator
To upgrade/downgrade a member follow these steps:
Locate the member within the “Users” page of your admin by doing a search for their name or email address. Once you locate the user, click their name or the edit link to manage their account.
On the edit user screen, you will see a section for “Membership Level” at the bottom of the page. Choose the preferred membership level from the dropdown list.
If you modify a user’s membership level through this method, their recurring payment will be cancelled automatically and they will no longer be billed for membership. To change a user to a paying membership, have them (your site members self serve and do it themselves) click the “change membership level” link under their account page.
Hope this helps
p.s Im not affiliated with Jason and his company im just trying to help those users of the plugin as I am a user of this plugin myself. :)