Mongoland Said:
"How to cancel a subscription to iHeart Radio Plus.: The only phone associated with the Apple ID that was used to purchase the subscription was stolen and will not be replaced. I am unable to verify who I am without the phone. So how can I cancel?"
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Two Factor Authentication:
You are able to log in to these forums. So, you must have used some sort of device to get in to it. So, does that device's key not work? If need be, add Two Factor Authentication to your computer. Go Here: Two-factor Authentication for Apple ID - Apple Support