If there is an instance that your account is on a monthly plan and you wish to cancel at the middle of the month, an invoice will be generated for the 30 day period. Post the 30 day period your subscription will be cancelled from further payments.
For example:
Billing date - 10.10.21, you wish to cancel on 30.10.21.
Invoice will be generated for 10.10.21 to 09.11.21