How can I uninstall the app?

For dummy products and variants:

• You can delete the bundles on the BYOB dashboard. The corresponding products will be deleted

For template files in your theme:

You can find the below files from your theme. There are:

7 section files:

• byob-bundle-info.liquid
• byob-confirm-modal.liquid
• byob-product-grid.liquid
• byob-footer.liquid
• byob-quickview.liquid
• byob-subscription.liquid
• byob-reviews.liquid

1 snippet file:

• byob-messages.liquid

1 product template:

• byob.json

After that, you can delete the app from your app list. If you are worried, you can make a backup before deleting the files. Even if you don't delete these files from your theme, there is no serious drawback. 

Your app charge

Once you delete the app, your account will  not be billed for the next billing cycle of the app subscription. Please check the billing cycle dates of BYOB as apps don't follow the same billing cycle as your Shopify subscription. Apps will follow a billing cycle based on the date that you install the app.

Everything about working with apps: https://help.shopify.com/en/manual/apps/working-with-apps

About your app subscription charges: https://help.shopify.com/en/manual/your-account/manage-billing/your-invoice/apps#subscriptions