The purchase of the Studo PRO version is handled either by Google (Android device) or Apple (iOS device), depending on the device you have used for the purchase. Studo does not process or store credit card numbers, PayPal accounts, Google Play accounts, Apple Pay accounts, Google Play credit, Apple ID credit, or mobile phone billings through Google Play or the App Store. Please change or update your payment methods directly
at the Google Play Store - how exactly does Google describe this at https://support.google.com/googleplay/answer/4646404
at the Apple App Store - how exactly does Apple describe this at https://support.apple.com/HT201266
If you have problems with your payment, Google at https://support.google.com/googleplay/answer/1267137 and Apple at https://support.apple.com/HT203005 will provide you with further help articles.
Greetings from your Studo Team