Once your return has been accepted (or mailed), it is too late to change your bank account for direct deposit.
If you haven't filed yet, you can still change your bank account info for the direct deposit, free of charge, by simply logging into your account, editing the details and clicking NEXT until the end so the updated documents would be generated.
If the info you provided is for a closed or invalid account, the government will mail you a refund check.
If the info you entered is someone else's account, don't worry - most banks won't deposit tax refunds into accounts where names don't match up.
The best way for you to track your federal refund is to call the IRS at 1-800-829-1040.