Try this if you haven't already. After you delete it out of your Nokia phone, make sure the headset is turned off. Then reboot your Blackberry. Make sure all other Bluetooth devices are as far away as possible. Once your phone is back up and running, hold in the button on the 975 until you see the light on the headset flashing red/blue, red/blue. Once the headset is flashing red/blue, you should be able to go into the settings and connections on your Blackberry and search for the headset. Once your phone finds the headset, your phone should ask you for a passkey which is 4 zeroes (0000).
If you still need assistance, you can contact the Technical Assistance Group at the following link: