Magento 2 Guest to Customer is the extension that allows you to convert guests to customers in your Magento 2 store. It has a lot of features such convert all old guest orders to customers or assign an order address to a customer and other.
However, the feature we want to discuss in this article is "Change Order Customer'. As the name of the feature implies, it allows you to change the customer assigned to the order.
e.g. you bought something as a gift and want this order to be assigned to that person because of the bonuses or account special offer, etc.
Once you change the order customer, you might notice that although the name and the email change, the billing and shipping address remain the same.
You can also see that it isn't changed in the order grid.
Even when you go to the customer account you've assigned that order to, you see that the order name isn't changed.
So, why doesn't it change if the feature clearly states "Change Order Customer"?
The thing is that you only change the order customer name. The billing and shipping address data is the information about the person that made the payment.
It is completely separate type of data and it cannot be changed automatically since it is important for accounting purposes.
If you want to change the billing or shipping addresses as well, just change it manually after you change the order customer.