Best answer by Dennis
One is the automatic topups from your credit card to your prepaid account. You set this amount and it happens every 30 days.
Second is the payment that is taken from your prepaid account that is used to buy topups and to renew your baseplan
So if you have enough funds added to your prepaid account, you can just turn off the automatic topups for a month or more or just lower it to below your baseplan amount and your prepaid account's funds will slowly dwindle