Change Gmail account to make in-app purchase?
To do so, you must install the app from the same google account from which you want to make the in-app purchase. Follow these steps,


Uninstall the app on the phone.
Go to the Play Store site in your web browser and find the app. Make sure you're logged into the website with the right account!
Install the app through the Play Store by clicking on ‘Install’ button (and selecting your phone).
Wait a minute until the app is installed on your device.
Make the in-app purchase.