Hi Heather,
You can change the customer on an order to the correct customer, as long as you have not saved the order. If saved, then you can copy the original order to the correct customer, and check off the appropriate boxes to apply the correct customer pricing with item pricing and information (for the correct customer). Then delete the originating order.
If you have not saved and wish to change to the correct customer, then if your OE template is enabled to allow you to edit price lists and customer type (which we would normally recommend), then you could revise the price list and customer type on the order header, but would still need to revise the pricing on the detail lines already entered. If you have a large number of lines already entered or cannot revise pricelist details, just save and copy the order as noted in the wrong customer (first) scenario, and check off the appropriate boxes to update to item pricing and information. Then delete the originating order.
Best,
Brian