By federal law, I'm needed on a number of my items that they need to be "Call to buyInch. It is possible to way will be able to disable the checkout process or at best the payment processing for specific groups on my small site and rather are requested to call customer support to accomplish an order?

Workflow ==> User finds an item he/she would like, will customize the colour along with other characteristics when needed, then they click continue or checkout but at this time an order is distributed to customer support and also the customer will be requested to call customer services to accomplish an order.

But that same client making and finish their order on the website for other items for example part and add-ons.

You may make an item say call to buy simply by enabling the inventory check and setting the merchandise inventory to . However, which prevents the consumer from adding the product towards the trolley. You'd need to hack the core considerably to offer the workflow you specify.