Subscription updates

Question:
[Can I cancel an already expired subscription? or amend it?]

Product:
[Plans / Subscriptions]

What are you trying to achieve:
[I have changed a subscription plan from custom one year that expired after this to a recurring annual charge but those that where already in the initial custom plan are being told “they have already purchased the plan and will be charged yearly until they cancel” ]

What have you already tried:
[Editing the current plan]

Additional information:
[How do I allow those customers to re-purchase their plan? or can I move the new annual subscribers to a new plan that the rest can purchase. Its a mess.]