@CCoupe85Which account are you talking about? Your Public Mobile account balance or your bank debit card / credit card balance? The payment system if required takes money from any balance in your Public Mobile account first, then if it need more money to cover the prepaid amount, it will draw on your bank / credit card balance.
If your autopay consistenly fails ie you loose service at the end of the month. You can try to put in another card. It is a weird quirk of Public Mobile.
@CCoupe85 , the self serve account always displays suspended status during the renewal process. The duration seems to have gone up a lot in recent times. What matters is that your service continues to be available through renewal. If you don't lose service, leave the account alone and let auto pay fo what it was intended to do.
It’s a good practice to manually add fund in advance, you will still get autopay $2 discount.
In your account, click on Overview, My Rewards, you will see "As of today your estimated payment is:" that is the amount you need to add in your account.