Creating service sales order / product sales order

SUGGESTED

I've tried searching for this and can't find any help so please excuse me if this topic and solution has been covered.

A couple of our members of staff seem to be creating "Service Sales Orders" rather than "Product Sales Orders"

I have no idea how they're doing this. We don't use 'service sales orders'.

1. I need to know how they are doing this, and how to to prevent them from doing this

2. I need to know whether I can change an order which has been created as a 'service' sales order in to a 'product' sales order.

Thanks in advance