Nokia 6120 & car kit

Hi
I have just taken out a new 18 month contract with 3 and I've got a new
Nokia 6120. I also have two plug in car kits (Parrot Easy drive and PMK5800)
unfortunately neither work with my new phone, so I rang up3 (Indian call
centre) and asked if it was possible to get a duplicate sim for my old phone
so that I could use it with one of the car kits. They told me that it was
not possible as the technology didn't exist to have two sims on one number,
but I'm sure I've seen when googling that vodaphone provide this service.
Does anyone have a solution short of buying a new car kit that would work
for me to save me having to put my sim in the other phone every time I use
the car?
Many thanks
Dave