They will not (or should not) give the pin out over the phone, otherwise any scroat who has just stole the unit could ring up for the pin.
When swapped my Rcd510 out, I went in to the dealer, with the serial number, and as long as you can verify you own the vehicle, then they should be able to get the pin in a few minutes.
I would be asking them for the official card, as it should have come with the car, along with the service book, user manual, etc.