Purchases are made through your iTunes or Google Play Store account from the app or by Credit Card from the web version of happn.
On the app, each platform offers you various payment methods directly from your account settings. Accepted payment methods may vary by country.
However, methods such as credit cards, gift cards or PayPal are usually available. For more information, please contact your store Customer Service.
Apple :
https://support.apple.com/en-us/HT202631
Google Play Store :
https://support.google.com/googleplay/answer/4646404?co=GENIE.Platform%3DAndroid&hl=en
You can also pay directly by Credit Card via Stripe.