Can't get my iPhone 4S to pair up via Bluetooth with the headset tried the instructions but does not seem to work

Should not be a problem. If you download the quick start guide from this site and follow the pairing instructions for your Bluetooth phone that should work well.
http://www.jbl.com/images/media/J46BT_QSG_EN.pdf

If you do not have instructions for Samsung Illusion then you can follow page 83 for pairing bluetooth in the manual from this site.
https://www.pagepluscellular.com/media/34912/Samsung_SCH_I110_Illusion_English_User_Manual.pdf

Not sure, If the manual, from the car radio says it should pair with Apple bluetooth devices, it must be a setup problem. If your radio is not (yet) compatible with MP3 over bluetooth from Apple devices, you should ask nissan if they have intentions to upgrade the software in the radio. I think you spent enough on your car, to get this kid of service.
I'm sure most modern car radio's are compatible, because my 2 year old Toyota Yaris can play my music and take my calls from my iPhone 4 without problems.

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Pairing with iPhone

1. Connect the iPhone Dual Dock or iPhone Bluetooth Travel Cable to a USB 2.0 port on your computer (not on the keyboard).
2. Connect iPhone and the headset to the dock or cable. The headset pairs with iPhone automatically.

Pairing iPhone Bluetooth Headset with another Bluetooth-enabled deviceTo pair the iPhone Bluetooth Headset with another wireless device, such as a Bluetooth-enabled phone or computer.
Step 1: Set the headset to be discoverable

1. Turn off the headset.
2. Press and hold the headset button for about eight seconds, until you hear the startup tone and then five quick high beeps.
   
   The headset is now discoverable and will remain so for about five minutes. The status light blinks while the headset is discoverable.

Step 2: Turn on Bluetooth on the other device and search for devices

1. On the device, turn Bluetooth on and set the device to search for other Bluetooth devices.
2. On the device, choose iPhone Bluetooth Headset and enter the PIN code 0000.

See the instructions that came with your other Bluetooth-enabled device for more information about pairing it with Bluetooth devices.

Detailed instructions can be found by downloading the user manual from the Jabra support page.
PAIRING IT WITH YOUR PHONE1 Put the headset in pairing mode- When you turn on your Jabra EASYGO for the first time, theheadset will automatically start up in pairing mode, i.e., it isdiscoverable for your phone. When the headset is in pairingmode the Bluetooth status indication on the StatusDisplay isflashing.2 Set your Bluetooth phone to discover the EASYGO- On your iPhone 4s, go to settings>General>Bluetooth and make sure Bluetooth is turned on.3 Your phone will find the Jabra EASYGO- Your phone will find the headset under name Jabra EASYGO.Your phone then asks if you want to pair with the headset.Accept by pressing Yes or OK on the phone. You may beasked to confirm with a passkey or PIN. Then use 0000(4 zeros). Your phone will confirm when pairing is completeand the Bluetooth status indication on the StatusDisplay willshift from flashing light to steady light and the headset voiceguidance will say connected.
Manual pairing modeIf you wish to use the headset with a different phone, or if thepairing process was interrupted, you can manually set the headsetto pairing mode.Make sure the headset is on. Press and hold the answer/end buttonfor approximately 5 seconds until the Bluetooth icon turns froma steady light to a flashing light. Then repeat steps 2 and 3 in theabove pairing guide.Connecting with your phonePairing is only needed the first time a headset and phone areused together. When the headset and phone have been pairedonce, they will automatically connect when the headset is on andBluetooth is activated on the phone. The headset can be usedwhen it is connected to the phone. If the devices are paired, butdo not immediately connect, tap the answer/end button. Whenyour headset is connected the Bluetooth connection icon in theSTATUSDISPLAY WILL BE CONSTANT ON FOR 3 SECONDS andthe headset voice guidance will say connected.

Once you make your iphone discoverable, then put the Plantronics 903 headset into pairing mode by pressing the power button until it flashes red and blue. If it's not flashing red and blue, it's not in the pairing mode. Below is a link for the user guide which has the pairing instructions:

Plantronics BackBeat 903 Pairing Instructions

Good luck from Headsets Direct!

As I have learned the hard way the iphone's bluetooth is only to pair with wireless bluetooth headset and car stereo. You cannot connect to any other kind of devices. Also you must have Iphone Os 3.0 or higher to stream music to your car stereo. If it still does not work then the belkin bluetooth audio receiver should solve your problen
http://www.blueplastic.net/en/escuchar-musica-de-tu-iphone-via-bluetooth-conectar-iphone-a-radio-de-tu-coche-via-bluetooth/

you need to download an application called bluetooth file transfer from the android market. it will help you with the file transfer via bluetooth

1)Turn on the bluetooth headset.
2) Turn on bluetooth on your phone. It starts looking for bluetooth devices in the vicinity. Your headset will be detected as "bluetooth headset" or "Motorola H12 Headset".
3)Once its located then select it and follow the onscreen instructions like choosing a passkey etc., to complete the pairing process.

put the music player on and press down on the jogwheel, select 'Play Via' and change it to Bluetooth stereo headset. It'll prompt you to open the swivel and take you to the bluetooth devices screen where you select the correct device, it'll then prompt you to close the swivel and will start playing through your headphones :-) Is that what you mean?... It's a bit of a pain really :-(