iOS In App Purchase: User Charged Twice for non-consumable?
===

My app sells non-consumable IAP products exclusively. The content itself is short videos, but quite a few of them so obviously they are stored in /Cache and not backed up.

I just received a complaint from a customer saying that "we charged him twice" for a product (as per iTunes invoice e-mail). This is not supposed to happen, since as I explained, all products are 'non-consummable'.

We explained him that it is Apple (iTunes) that manages payments, etc. and we only provide the content, so any support should be directed at Apple/iTunes.

Still, I am worried that this kind of thing could happen any often. I searched the web but only found this case:

http://forums.toucharcade.com/showthread.php?t=97184


I couldn't find any relevant section in any of Apple's FAQ or support pages (aimed at the user) or the developer forums (aimed at the developer).


Assuming this is a (rare) bug in iTunes, does it happen often? 

If you have any similar experience to share, and how you solved it, it would help...