Bluetooth BTW-5018

I purchased this universal Bluetooth BTW-5018.
I am using it with NOKIA 6600. For the first 4 months it worked fine
except that the MIC does not pick the voice clearly...so the person on
the other side keeps asking U to talk louder.

Now the strange problem is when I try to coonect it, the NOKIA 6600
keeps asking for the (passcode for BTW5018 )...I did not set any
passcode, so I am unable to use it anymore...
I tried on-and-off the phone, I also reformatted the phone..but the
problem is still there...
please guys any advice ??