If you don't want to get charged next month, you must cancel your plan before the end of your billing cycle. So, if your billing cycle resets on the 5th, you have to cancel before that date.
If you cancel after your billing cycle restarts, you are responsible for that month's payment. We do not offer refunds for late cancelations.
That said, you can cancel your plan whenever you see fit. Heepsy's subscriptions do not have any minimum period of commitment.
If you cancel your plan, you can continue to use it until the end of your billing cycle.