When placing an order, the customer can check the Do not call for order confirmation box.

You can also alter the tooltip text for the customer.

After the feature is enabled, the corresponding field appears in the order information in the admin panel.

The feature is enabled in the Settings → General settings → Checkout section of the admin panel.

In the same block, you can also edit the tooltip text or hide it by removing all text from the input field. In addition, you can make the "Do not call to confirm order" box checked by default for all customers.