This plugin allows preventing users subscribe to a subscription plan if they have active subscription of other selected plans
To use this plugin, go to System -> Plugins, find and enable Membership Pro - Plan Subscribing Restrictions plugin. Click on it to edit, setup the parameter to have the restrictions you want:
For example, with the setup in the screenshot, if someone has active subscription of 9 Months Membership or 12 Months Membership, he won't be allowed to subscribe to 6 Months Membership plan.
