Thank you for reaching out to the Community! I'm happy to provide some assistance with the shop's domain, to ensure this gets resolved. To confirm I'm fully understanding, are you looking to disconnect a custom domain (i.e not the .myshopify.com URL) that you've purchased from the shop?
If so, we have a great document available that touches on how you can complete this. It will allow you to disconnect a custom domain if you no longer wish for it to be associated with your Shopify store.
To complete this, you can:
Head to Settings > Domains, from the Shopify admin.
Click the name of the domain that you want to remove.
ClickRemoveagain to confirm.
Once the domain has successfully been removed, you can then can change your DNS settings in your domain provider account to point it to another website.
Please let me know if you have any other questions or concerns.
Blair | Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog