Yes. As long as your order has not entered the "shipping" stage, then you can make a change. To request a change, simply submit a support ticket along with your order number, full name on order and email used on your order.
Keep in mind, if you change the shipping carrier or shipping speed, additional costs may apply and MUST be taken care of before we can ship out your order. If a refund is owed after you make your change, then it will be applied to your account.
If you need more information, have additional questions or just can't find the answer to your question here, please submit a support ticket and one of our account managers will be happy to help.