Add Two Payment Gateway Xamarine Android App

I have a video app built in Xamarine Android. It has two two of videos: Free Videos and Featured Videos. Free Videos will be free, but Featured Videos will require that user subscribe before they can watch videos. Subscription Packages will be 3months, 6months and 12months. When user clicks to watch any of the FEATURED Videos, the video will play for for the first 5minutes and after that, the app will call the SUBSCRIPTION PAGE and users will have to subscribe before they can continue watching. They two payment gateways to be use for payment are PAYSTACK and Google Playstore In App Purchase.