To unlink iHeartRadio with Alexa:

1. Visit the Alexa app on your mobile device
2. Tap on the Menu (More) button 
3. Tap on Settings > Music and Podcasts
4. Under Services section find and tap on iHeartRadio
5. Tap on the Settings button
6. At the bottom of the Skills Settings page tap on the Disable Skill button.

For further Amazon Alexa support visit the Amazon Support Center.