It may also be that the account you used with the App Store app on your iPhone is not the same as the one you're using with iTunes. If so, and you don't want to change that, then just get the upgrade directly on your iPhone via the App Store application.
email@example.comPlease read the documentation and check the FAQs first. Make sure you have the latest version (see the Release Notes); it's displayed at the bottom of each Help screen. We try to respond quickly but we're only a two-person company so occasional delays are inevitable.