I think your dealer is telling porkies there.
Have a look in your service schedule (book 1.1) inside cover will have your vehicle data PR numbers. Look to see if you have QG1, this indicates service interval prolongation which means 15,000km oil change (also noted on page 7). Unless you are using diesel with a high sulphur content, are a taxi, regular towing maximum weight trailers or exposed to high levels of dust all the time then 7,500km oil changes are not required.
Myself and all the other owners of V6 TDI (facelift model) Touaregs I know of have not had their dealer try this on us.

I would suggest ask the dealer why they require this service to be conducted and if the answer is not to your complete satifaction question it. Also try another dealer for their advice on this issue. Unless this is a free service by the dealer then go for it.

Flipper Dog