Top 5 Easy Ways to Delete Duplicate Contacts on iPhone 
Open the Phone app on your iPhone then tap on Contacts.
Search and open any duplicate contact present in your contact list.
Tap on the Edit button to make changes.
Scroll down to the bottom to locate the Delete Contact option
tap on it to delete the duplicate contact.
That’s it. You’ve successfully deleted a duplicate contact manually on your iPhone
Alternatively, you can merge all the duplicate contacts into a single contact profile by tapping on the Link Contacts option