Canceling a Pandora account is something that can be done quickly from within an official Pandora app and on the Pandora website. This article explains how.
How do I delete a Pandora account?
If you listen to Pandora on an iPhone, iPod, or iPad, follow these instructions to cancel your Plus or Premium subscription.
Open the iTunes program on your computer or smart device.
Click on Settings, followed by iTunes & App Store, and then select your Apple ID.