DB9 sat nav NO VOICE GUIDANCE

[Loft 0075]

Hi

I have a DB9 (2006) that was originally supplied in the USA.

It came with a genuine AM West Coast American sat nav map disc, and while the maps were no use the voice function worked. (It would say things like "you have not set a destination")

So I purchased two UK/Europe dvd's.
First a volvo disc, then an Aston version.

Neither of them will play voice commands or voice guidance.

I'm now being told by the disc provider that I need to get Aston Martin to upgrade my sat nav firmware because the car is American.

Are they right?
Can anyone advise?

(And I do want the original sat nav working fully, not resort to a Tom Tom)

Thanks