After customizing a subscription, you can revert back to the original plan by synchronizing it. This will unlock the subscription, so that any future changes made to the plan will apply to the subscription.
1) Go to Subscriptions.
2) A subscription that has been locked from synchronization will have this icon next to it. Click the locked subscription.
3) Choose Unlock & Sync.
That's it! Now you know how to unlock and sync a subscription.