HI can anyone help

I have a strange noise coming from the alternator, i have been told it could be the bearing in the pulley. I spoke to Chrysler an was told that you cant just change the pulley you have to change the whole alternator £580 +fitting if its a Bosch or £720+ fitting if its a Valliant, what a rip off the cars only done 24,000 miles and is not even 4 years old yet, Has anyone just changed there pulley. Thanks