Can I cancel or change an electronic funds withdrawal payment after the return is sent?

You will want to call the IRS e-file Payment Services at 1-888-353-4537. They're available 24/7.

Of note:

• Once the return has been accepted the information pertaining to the payment, such as the account information, payment date or amount cannot be changed.
  • If changes are needed, the only option is to cancel the payment transaction and choose another.
• To inquire about or cancel a payment wait 7 to 10 days after the return was accepted before calling.
• Scheduled payments can be canceled up to 11:59 p.m. ET two business days before the scheduled payment date.  The cancelation must be authorized by the taxpayer.

For more information, see here.