I have a mobile app on iTunes https://itunes.apple.com/us/app/ja
We keep having this problem where users enter valid credit card information but the app still declines the transaction. Something is wrong where not all valid payments are being processed.
I can provide source and server things to help you figure it out. I can also provide anything I already know. The payment gateway is authorize.net
The app is live and makes money so I am looking for someone who is skilled in fixing problems the first time. If you are skilled I will also have other work for you as the Android version has bug problems as well.