Hi - I don't have a Sonata, so I can't verify this solution, but it was sent to me by email, so I thought it worthy to share:
How to pair your iPhone 5 with a 2011 Sonata, transfer your contacts, and get voice recognition working ...
Start car, put in park. Push the setup button on the radio panel, scroll to BT (Bluetooth), push knob-in to select. Then you get a BT pairing password (4 digit)on the display. Now, go to your iPhone 5 and tap settings, go to Bluetooth, Sonata should come up under the heading ''Devices"- touch Sonata to select - and a keyboard will be displayed. Enter your BT 4-digit pairing code. Now your car & iPhone 5 should be completely paired. Go to your contact app on your phone and click groups - check only ONE group and that contact list should automatically transfer to the car. (If not, try turning the car off and then back on.) After Bluetooth connects you should see (In the settings Bluetooth display) "Transfer Complete." Now, you should be able to make a call by pressing the Command button on the steering wheel and the voice-recognition will ask if you want to call by number or name. The call will go through when you say, 'Yes"... (Or whatever the voice says follow directions - it will recognize your voice.)