Code solution to prevent production in app purchase from using sandbox?

I have an issue where a live app is using in app purchase. Everything tested well and for the most part seems to be working well in the app sold from iTunes.

Recently I have had 2 reported cases of users who cannot use in app purchase in the live app because iTunes is asking them to purchase from the sandbox. The sandbox requires a test account and not a real account, which they of course do not have.

In both cases the users themselves are also developers. I am the developer of the app and purchase from within my app, without issue.

Is t开发者_StackOverflow社区here a code solution to force my app to never use the sandbox for in app purchase?

Is my app's in app purchase code missing something?

Or is it the other developer's phone confusing iTunes and there is no code solution?

It was my understanding that this should be auto detected by iTunes.

---

The PocketMoney app had the same problem according to their blog and traced it back to being due to having a jailbroken phone with AppSync installed.