This depends on which IRS department is handling your case. Your IRS notice will usually be a good indicator of who is assigned to your case. If you are setting up a payment agreement with the IRS that is not an extension to pay or a streamlined installment agreement, you will always need to deal with IRS Collection.
If you receive a notice saying your case is assigned to IRS Collection, call the IRS Automated Collection System unit at (800) 829-7650 (wage earners) or (800) 829-3903 (self-employed).
If you aren’t assigned to IRS Collection and want to set up a streamlined installment agreement, call the IRS at (800) 829-3922.
If the IRS assigned you a revenue officer, you’ll need to work directly with that person to get your agreement.