Exchange Contact not showing/merged?

Hi there,

I am having an issue with contacts when connecting Android devices (I have tried with a Lenovo Tablet as well as a Galaxy S5) onto a specific exchange account.

It connects fine. Sync's the mail ok. But on Outlook, the user had 6970 Contacts. On the device, it only pulls through 5670.

I have tried deleting the account and re-adding it. Changing all the sync settings to push, manual and everything in between. But still misses off more than 1000 contacts.

When I looked on the device to try find a particular contact that was not appearing it seems as though the android device took it upon itself to merge 2 contacts that had the same phone number, but different names and e-mail addresses into 1 contact and gave it the name of the first contact with that number.
I believe he has quite a few like this where they have different names, but one or more of the phone numbers (or possibly other details) are duplicated on some other contact. And so I think this is likely to be the problem... unless anyone can tell me different?

Is this something that can be gotten around? Or is there a way for it to break the contacts back apart? Or is it just a fact of life that multiple contacts with the same phone number will be automatically merged into 1 contact?

It is a hard one as the user has both a Blackberry and an iPhone (I only just got him to change to Android as his main device as well!!), which both seem to leave the contacts as they are. So that is what he is comparing it with and expecting it to be like.... and without going through every single contact to show him that they are indeed all there, just merged, I know he is always going to calling me back into his office over "missing" contacts.

Any help is greatly appreciated.