If you need to get your iPhone contacts under control and the stock contacts app is not doing the job for you one of this two powerful but free app can get the job done.

Both Circleback and Fullcontact have clean model UIs and both offer extra features like contacts backup and sync.

I have used both and like both and for personal preference stayed with Circleback but I will recommend you try both as both  are full featured.

First We Have My Personal Choice Circleback - (DOWNLOAD FOR iOS HERE)

This app offer the following features (and no in-app purchase)

It will automatically update contact details when people in your network change phone number, jobs etc. 

Plus

• Intelligently merges & manages duplicate contacts

• Automatically stores & completes contacts from email signatures in Outlook/Exchange and Gmail

• Offers contact grouping by favorite, old/archived, or business card scans 

• Saves Outlook/Exchange, Gmail (Google), Facebook, LinkedIn & other contacts into one complete address book

• Syncs contacts across multiple devices & platforms

• Exports updated contacts to Salesforce & Act

• Scans business cards with the most accurate scanner on the market

Second We Have Fullcontact (DOWNLOAD FOR iOS HERE)

Now Fullcontact is an amazing app too but I was no fan of the paid upgrades via in-app purchase but thats because I only had a little over 100 contacts to manage and did not need the extras. If by contrast you have hundreds and hundreds of contacts then Fullcontact maybe a better choice for you.

The app features 

COMBINE & SYNC CONTACTS
• Combine address books - combine multiple Google Contacts, iPhone contacts, social media accounts & more
• Backup contacts - safely store your contacts in the cloud
• Keep in sync - sync your contacts across multiple devices

ORGANIZE & CLEAN
• Merge duplicates - automatically de-dupe your contacts
• Add tags & notes - sync tags & notes across devices

FULLY CONNECT
• View photos - automatically add photos to all your contacts
• Add context - connect social media profiles, titles, and more
• See company info - learn more about your contacts' workplace

Some Of The Premium Features Available With A Subscription via In-App Purchase. Note that this features are included on Circleback for free.

• Scan business cards - add contacts with just an iPhone photo
• Capture email signatures - update your contacts from their email signatures
• Sync multiple accounts - sync up to 5 address books

In short both are great apps. I personally prefer Circleback and think it is enough for most people. But for those with a big list of contacts to manage then Fullcontacts may be a better choice.