To set the Commission for an Agent, first assign their Call Center to a phone campaign. This can be done by editing your call center.
Click on CRM >Call Centers in the navigation Side Bar. Then click on the blue Edit Icon.
Click on the green + Button to Add Campaign. Choose the appropriate campaign from the drop-down menu and then click on the green Add Campaign button.
Once you add a campaign, you can then Add Agents and apply their commission rate.
Alternative
You can set Base and Upsell permissions per campaign. To accomplish this, navigate to CRM → Campaigns then click on the blue Edit icon of the campaign you added in the Call Center in the previous steps.
Scroll down to the Call Center section and click the blue Edit Icon
The fields to add both Base Commission and Upsell Commission rates will be displayed. Click on the Update Button to save the changes.