Product changes take effect when your subscription renews. No changes are made automatically to outstanding shipments. If you want the change to take effect immediately, you will need to contact the seller by clicking on the Contact Seller button on their Cratejoy Marketplace listing.
Log in to your Account page and click "Subscriptions"
Click "Manage Subscription"
Click "Modify Plan Details"
You will then be taken to your customer account page on the Seller's website. This page lists all subscriptions you have for just that store. Here you can change the product for you subscription.
Click "Edit" on the subscription you want to modify
Choose the new product, variants (if applicable), the term, then click "Change", and "Confirm"