Nokia 5230 :: Sync Contacts - To Remove Duplicate Enteries?

I have the latest version of OVI on my PC which I use to SYNC CONTACTS. Problem is it DUPLICATES the contacts on my NOKIA 5230 even if I DELETE all the contacts listed on the PC OVI list. My understanding of SYNCing is that the PC and the NOKIA should have the same information. Either the SYNC is not working or there is a setting somewhere that needs to be changed? MY NOKIA is showing over 500 contacts when it should be half. Manual deletions to remove all the duplicates is a long job and the SYNC process always returns it back to over 500.I have set my NIKA to save all contact to the Phone Memory (not the SIM). Any ideas of to avoid and remove the DUPLICATES.