QB Online is a subscription product. You have to pay it monthly or annually. If you have to open a new QBO account, make sure to click the Buy button to get the discounted price for up to 6 months. If you purchase from the trial account, you have to pay the regular price. Plans & Pricing.
At this time, QuickBooks only accepts debit and credit cards like Visa, MasterCard, and Amex. Thus, changing the payment method using a Net Banking account isn't available.
Just in case you're ready to update your payment method using a different credit card, you can read this article here for more guidance.
For more information about the payment options, as well as how to upgrade or downgrade your subscription, I recommend the following articles: