You must change your billing information on the platform where you signed up for your subscription - either on the App Store or on our Desktop Site.
Check where you signed up on the iOS apps:
Tap on Profile in the bottom menu bar
Tap on your Collection in the middle of the screen
Tap "Subscription". A pop-up will appear explaining what platform your subscription is affiliated with.
If you purchased on the App Store:
If you pay for InVintory through the App Store, all your payment information lives with Apple.
Just update the credit card associated with your Apple ID.
If you purchased on our Desktop Site:
Click on your collection.
Click on your subscription.
A new billing window will open. Click "Add payment method" towards the the right side.
Enter new card details and "Update"