You're welcome to connect Pipedrive as conversion tool by going to Settings > Conversion Integrations > Pipedrive > Connect.
After you've connected Pipedrive with Attribution app your Pipedrive contacts will automatically become identified visitors in Attribution app. Any changes to your contacts will be tracked in Attribution app as events.
Changes to a deal
Any changes to your deals will be tracked as events. When you mark a deal as 'won' in Pipedrive it will be considered a 'conversion event with revenue' and be used to calculate return on ad spend. If you'd like to send a refund you would simply need to make the deal value a negative value by adding a minus in front like '-$200'