You may have an easier time canceling the payment you scheduled through the Direct Pay website - go to the site below and lookup payment (hopefully you kept the confirmation number). If the payment hasn't already been processed in the system, you might have the option to modify or cancel it.
For the payment sent with your return through TurboTax - once the return is filed and accepted its in the hands of the IRS and you will have to call the IRS's payment services hotline to cancel any automatic payment you have scheduled.
"Call IRS e-file Payment Services 24/7 at 1-888-353-4537 to inquire about or cancel your payment, but please wait 7 to 10 days after your return was accepted before calling."
Note: They advise waiting 7-10 days after the return was accepted to ensure the information is in the system, but you will want to try to call now since your payment is scheduled sooner.
