If you decide to cancel the subscription after attaching a card, then cancel it before the free trial period. If you forgot and the money is charged, a refund is possible only during the first month after payment then the refund will be credited to the original mode of payment withine 7-10 business days.
If you cancel your subscription and it happens to be in the middle of the month/year when you have already paid for the whole month/year, you will continue using all your features by the end of the month/year. StemEZ cannot refund the money you have already paid.