Why did you charge me twice for buying an italk app?

We didn't charge you for anything, we are fellow users and these are user forums, not iTunes Support nor Apple.

If it shows twice on your iTunes account's purchase history (i.e. one 'charge' isn't just : About payment card authorisation holds in the iTunes Store - Apple Support) contact iTunes Support e.g. via your purchase history, the emailed receipt, http://reportaproblem.apple.com or https://www.apple.com/emea/support/itunes/contact.html

I was hoping somebody reads it from iTunes, or Apple

You already knew that these are user forums, you won't get an answer from either iTunes nor Apple on here