I know this is an old thread, but I wanted to give a little more detail for anyone who has the same problem.
If you installed OWA on your iPhone, all of your Exchange contacts will have been duplicated on your phone locally via an OWA group, then linked to your Exchange (Office 365) contacts. To remove these duplicate contacts, here's what I did:
- Back up your iPhone
- Go to Settings - Mail, Contacts, Calendars - Exchange
- Turn Contacts off (Now only the OWA contacts will remain)
- Go to Settings - Mail, Contacts, Calendars - iCloud
- Turn Contacts on
- Go to https://www.icloud.com/
- Log in with your Apple ID and PWD
- Delete all contacts plus the OWA group
Now there should be no OWA contacts on your iPhone
- Go to Settings - Mail, Contacts, Calendars - Exchange
- Turn Contacts on
Now you should have ONLY your Exchange contacts and no residual links to the OWA contacts.