I have followed all your steps, but am unable to cancel a subscription to iHeart radio. Can you help me?

Have you tried following the steps in this article?

View, change, or cancel your subscriptions - Apple Support

If you are still unable to stop the subscription:

Contact Apple for support and service - Apple Support

Follow the steps in the support document linked to by Androish above and see if you can find the subscription.

If you can't. Then the next step would be to make sure the email you received was actually from Apple, and not a scam or phishing attempt.

Identify legitimate emails from the App Store or iTunes Store - Apple Support

What steps did you follow exactly?

What happened when you followed them?

Did you get any errors?

Was there something wrong with the steps you followed?