Occasions retrieves all the contacts from the device's Address Book, so if you're seeing duplicate entries in Occasions, there are also duplicate entries in your iPhone/iPod. Apple has a great support document detailing how to help resolve these duplication issues:
This is caused by a syncing and setup issue between the device and the program or service with which it syncs with. There are three main issues we know of which may cause this:
The root cause of this issue is that the dates stored in the device have time zones and the time of the day stored within them. If the program or service with which you sync doesn't handle these in a proper way or changes these values (which are not visible or modifiable to the end user), dates can shift around. Please contact Apple support or your service provider for ways to help alleviate this problem.
If a date is added outside of Occasions, the scheduled notifications will not be updated with the new date(s) until you run Occasions so that it can reschedule the notifications.
If you are experiencing a problem with one of our apps or with your device, in general, please try shutting down your device and restarting it. Rebooting a device can solve quite a few issues, especially if it’s been a while since your last shut down/restart. To shut down: hold the lock button until “Slide to Power Off” appears, then swipe.
Please feel free to email us.