How I can stopping in App purchase?

If you mean how to prevent in app purchases:

Prevent in-app purchases from the App Store - Apple Support

You can request a refund by following the steps in this guide:

Request a refund for apps or content that you bought from Apple - Apple Support

You are not guaranteed a refund tough.

This is an automated possess, if you wish to talk to a person you can:

Contact Apple for support and service - Apple Support

Good luck!

contact iTunes Support to see if they can/will help. See the Apple Support articles below for contact information.   

iTunes Support – world wide 

Apple Support schedule phone call       

If necessary, try Twitter

https://twitter.com/AppleSupport.          People have posted it may take an hour or more to get a response.