1- On your blackberry, go to: www.google.com/mobile/sync and download and install the application “Blackberry Sync”. you can also find this in the “blackberry apps world”
2- after installation is completed. run this application, Enter user’s gmail account, and click Sync now.
3- Wait untill all contact uploaded in gmail. note that, these contacts will be merged with any existing contact in the gmail.
4- On your computer, go to www.google.com/contacts and make sure your Blackberry contacts are all there.
5- On your iPhone, go to Settings->Mail, Contacts, Calendars->Add Account->Microsoft Exchange. Enter gmail address; Server: m.google.com; and leave Domain blank
6- Select contacts to be synced to the iPhone.
You are all done.