Outlook contacts duplicate on iPhone and all iOS devices

Question

Hello,
I have been having this issue for quite some time and I have not been able to find anything that would solve my problem besides deleting the contacts manually.
So here is the deal:
In our business environment we use all kinds of iOS devices (mostly iPads and iPhones). So what happens is (at least in my opinion) outlook somehow duplicates the contacts and since we have the outlook contacts to sync on the phones and ipads, they also duplicate on the user's devices. This issue happens about every 2-3 months. When I go in and delete the contacts manually from Outlook, the contacts from the iOS devices sync with the Outlook contacts and the duplicates disappear, but sometimes I have to go in and manually delete them from the devices as well. It is really frustrating for the users because this issue happens often as I said.
The issue happens on iOS 6, iOS 7 and on iPhone: 4,4S, 5, 5S, iPad: 2, 3
What I've tried:
1. I deleted all the contacts manually and made sure they sync with the Outlook contacts.  - WORKS TEMPORARILY
2. I turned off iCloud so that the contacts don't replicate among other devices using the same Apple ID  - DOES NOT WORK
3. I deleted the duplicates and told the phone to sync less often not as soon as there is a change - WORKS BUT AFTER TIME STILL DUPLICATES
4. I contacted Microsoft for help with the issue and they told me that the issue is probably an iOS issue. - NOT REALLY SURE
Any help would be a appreciated it. I want to solve this issue once and for all.

Answer 1

After getting your Address Book contacts restored on your Mac, the Address Book application includes a simple backup feature.
At the menu bar, go to File and select Back Up Address Book.
The default name for the backup file will be Address Book - (and the date).
Store this file in a safe location - preferably on an external drive used for backup purposes only.
If you ever need to recover all Address Book contacts from the most recent backup file, at the Address Book menu bar go to File and select Revert to Address Book Backup selecting the Address Book backup file.
iCal includes the very same simple/easy backup feature.
Before using a sync type function with any device, creating a backup of the data to be synced is a good idea and should be your very first step. The same before making a number of changes, additions, deletions to the Address Book data. This shouldn't happen so something is wrong but it can happen which is one of the reasons for maintaining a regular backup of all important information.