You will want to call the IRS payment services to cancel your scheduled debit or at least to confirm its been cancelled. Its possible it may have been cancelled once the installment agreement was set up, but it is not necessarily automatic and you don't want to risk the full amount being withdrawn when you aren't expecting it.
Once the return is filed and accepted, you will have to call the IRS's payment services hotline to cancel any automatic payment you have scheduled. They advise to wait 7-10 days after your return was accepted before calling to give the system time to reflect your information.
If you have any issues using the above number, you can also call the regular IRS number at 800.829.1040 to speak to a regular customer service representative.
