In order to cancel a subscription, you must contact Microsoft customer care.
You have 30 days to cancel your subscription after placing your order during the initial subscription term, but you will not be refunded for the first month of your subscription. If you choose to terminate your subscription after the 30-day cancellation window during the initial subscription term, you are not entitled to a credit or refund for that subscription term.
Cancellation Policy for Subsequent Subscription Terms
After the renewal of the first subscription term, you can cancel at any time with a minimum of one-month advance notice. After giving notice you will be charged for a final one-month subscription fee.