Duplicate contacts

Remove duplicate contacts

1. Make a copy of your contacts.
2. Open Contacts.
3. From the Card menu, select Card > Look for Duplicates.
4. When asked, click Merge.
5. Repeat steps 2 and 3 until no duplicates are found.
6. Make another copy of your iCloud Contacts.

If you see duplicate contacts after setting up iCloud Contacts ...

Contacts are neither stored locally on an iPhone nor in SIM. They are synced to an email account that you had Google, iCloud, AOL, Exchange, Outlook, Yahoo or any Other

How many email account you have added to your device and enabled contacts? Probably they have duplicate contacts between the email accounts. Remove one of them.