Yes. There is no minimum term so you can cancel your subscription at any time, provided the specific service is in a cancellable state, e.g. there is no balance on the account. If there is a balance, this must be cleared before the service can be cancelled.
If you cancel the subscription part way through the month, you will not receive a refund of your monthly subscription fee and your account will be terminated immediately. You may therefore prefer to cancel on the last day of the month. If you cancel before your first monthly subscription fee has been taken, you will still be charged your first month’s subscription fee on the first of the following month.