how can i check if i have unpaid orders?

Hi there

Try this:

Add a new, valid payment method, then remove the old payment method. If you have an unpaid balance, the new payment method is charged automatically. When the outstanding balance has been paid, you can make new purchases or use subscriptions again.

Change your payment method

Use an Apple Gift Card or App Store & iTunes gift card to pay an unpaid balance

1. Purchase an Apple Gift Card or App Store & iTunes gift card.*
2. Redeem the gift card.
3. On your iPhone or iPad, open the Settings app, then tap your name.
4. Tap Media & Purchases.
5. Tap View Account.
6. Tap Purchase History.
7. Tap the order with red text that says Amount You Owe.
8. Tap Pay with Apple ID Credit.

After you pay for the unpaid order, you can make purchases with your remaining Apple Account balance.

* Gift cards aren't available in all countries or regions.

If you use Family Sharing

If you use Family Sharing and purchase sharing is turned on, the family organizer's payment method is charged for all family members' purchases. If you're the family organizer and you or a family member can't make purchases, change your payment method.

If you're not the family organizer, ask the family organizer to change their payment method. Or redeem a gift card and pay your unpaid order.

See this link for further reference

If a message says 'billing problem with previous purchase' or 'verification required' - Apple Support