Payment information is stored with your Apple ID or in Google Play and we never have any of your information.
Here's how to change your payment information on Apple Devices
Open the Settings app.
Tap your name at the top.
Tap Payment & Shipping. You may be asked to sign in with your Apple ID or use Face ID/Touch ID.
To update an existing card, tap the card you want to change and select Edit.
Enter the new billing information, including the new card number, expiration date, and security code, and then tap Done.
To add a new card, tap Add Payment Method.
Here are Apple's instruction which includes more information for different devices.
Here's how to change your payment information on Android Devices
Open the Google Play Store app on your Android device.
Tap your profile icon in the top-right corner.
Tap Payments & subscriptions, then Payment methods.
Select More payment settings.
Sign in to Google Pay if prompted.
Under the payment method you want to change, tap Edit.
Make your changes and tap Update.
To add a new card, go to Payment methods in Google Pay and click Add payment method, then follow the on-screen instructions.
Here are Google's instruction which includes more information about their payment options.