Do you use Shopify Payments to accept payments, and is it the bank account linked to your Shopify Payments account you're trying to change? If so, you should be able to do this in Settings > Payment providers. You can enter in a new bank account in which you'll receive payments by confirming the details of both the current bank account you have on file, and the new one.
Please let me know if you have any issues doing this.
Victor | Shopify Social Care