Salespeople can change Sales orders in a number of ways through "Portal". There is however a limit to what can be changed in portal and anything you cannot change yourself through portal can often be done by either Order Management or the WHSE.
The following changes can be made in portal to "Open" orders;
"General" Window.
*May not affect every billing address line - good to email OM also to follow up with changing invoicing details on Sales Orders.
"Shipping" Window.
"Lines"
"Requested Delivery Date"