As you may have seen our default widget supports the one-time purchase option, too.
You can easily hide it by following this instruction if you want to sell your product only by subscription:
Go to your store's Shopify admin panel
Go to Products
Go to the specific product you want to remove the one-time purchase for
Scroll down to the {Purchase options}
Check "Only show this product with these purchase options"
6. Save it.
This gif shows the procedure mentioned above:
