Have you already e-filed your return? If so, then you will not be able to change your bank details. You will have to wait to see if your tax return is accepted or rejected by the IRS. 

If the return is rejected, then you can update your information and resubmit your return. Should the tax return be accepted and the IRS (and State, if any) cannot deposit your refund to your account, then a paper check will be mailed to you.

You can refer to this TurboTax FAQ for complete information:

https://ttlc.intuit.com/replies/3302459