There will, unfortunately, be members who no longer want to continue with membership -- it is part of the business.
Members can either cancel their own membership online, or you, as the administrator, can cancel membership for them.
Members Cancelling Their Own Membership
There are three ways members can cancel their own membership to your iGrOOp.
When a member is cancelled or cancels, although their profile is removed from the group, all of the contributions such as postings, blogs, galleries, etc. will remain. These are NOT deleted.
If you are using the affiliate module, and a member cancels who is the result of an affiliate, that affiliate will automatically no longer get commission for that account.