Sure - have the clients check their bank statements.

https://www.irs.gov/payments/pay-taxes-by-electronic-funds-withdrawal#:~:text=Call%20IRS%20e%2Dfile%....

• 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.
• Cancellation requests must be received no later than 11:59 p.m. ET two business days prior to the scheduled payment date.