How do I cancel my subscription?

Sounds like you. May be referring to hot to cancel a HealthTap subscription. If so reach out to the support line. They should be able to guide you through the process.
Depends. What sort of subscription? Is this to a periodical, a recurrent receipt of merchandise (e.g. chocolate of the month club), membership like in a gym, web site email (like spam) or some other recurrent item. Find the email or mailing address or phone number associated with your subscription and contact them for cancellation and hopefully a refund.