How do I modify the the incoming/current call popup? I can modify other call pages but not that one.

How do I modify the the incoming/current call popup? I can modify other call pages but not that one.

I want to modify the incoming and active call popup on the crm to include customer relevant information, such as purchase history or length of relationship.  Under modules and fields, I don't seem to see active call as a choice to modify, only the main call page, and the after-call card.  Please advise