Removing annual membership

Hi everyone!

I’m removing the annual tier from my Ghost publication (Ghost 4.0). All good on the settings & theme so far but I’m wondering how I should handle existing annual members on Stripe so they can become monthly members when their subscription expires.

I’m thinking of giving them on Stripe the monthly membership with X amount of days in free trial according to their current renewal date and cancel(?) their annual subscription. But what will it look like on Ghost?

Please help!

Thank you,