Sometimes our members pay offline for an upgrade.
In these cases, we perform an upgrade from the backend by clicking on the "Upgrade subscription" option after clicking to see the subscription detail.
The upgrade works as expected. However, the existing plan is NOT expired, leaving the user with 2 subscriptions.
This becomes a real problem when a user upgrades a 1-month subscription to a 3-month subscription, as when the existing 1-month subscription expires the effect is to make them a free member, even though they still have 2 months left on their current subscription.
When a plan is upgraded, the old plan should be replaced or expired.