If you've already Efiled, you can't change your Direct Deposit Info.
If you haven't, you can change your refund info by going thru the FILE section until you come to a page, How Do You Want Your Refund?
If you're using TurboTax Online, close the program, clear your Cache and Cookies and return to the FILE section.
Here's how to Contact TurboTax Support for more help.