Someone at a customer had purchased a Project 1 License themselves via the Self Service Portal ( which lets a User purchase a license using a company credit card instead of an Admin purchasing it ) 

The user had left so the company still got the bills through, there is no native way for IT Admin to cancel this in the 365 dashboard, you either have to speak to 365 support to do this OR we reset the users password and log as them to cancel

Whats the reason for Self-Service? So large enterprises can move license procurement and purchases back to cost centers in their business’ via Credit Card and expenses instead of managing it internally 😉

Self-service purchase FAQ | Microsoft Learn

What happens to a self-service purchase if a user leaves the organization?

If the person who originally bought the self-service purchase product leaves the organization, valid users continue to have full use of the product for the duration of the subscription. The subscription remains active until the purchaser directly cancels it or an admin requests cancellation of the subscription through customer support. Admins may also choose to assign a centrally purchased license to users of the canceled subscription.

How to cancel a Microsoft 365 subscription

Reset User who purchased Self Service License Password if they have left. Login and go to the Manage subscription page , Select Cancel subscription (it might say Upgrade or cancel).