Unfortunately, once your e-filed return has been accepted or you already mailed it, it's too late to change your refund account.
If you entered a valid (but incorrect) account number not belonging to you, usually there's nothing to worry about, as many banks won't deposit tax refunds into accounts where names don't match up. You can try calling the IRS to stop the direct deposit if your return hasn't posted to their system yet (and you're willing to get your refund via paper check).
If your account has been closed. The bank will reject the refund and send back to the IRS. Once it is sent back, the IRS will issue you a paper check within 2 weeks.