You don't even have to pay a visit to the dealer...a quick call to A8 Customer Services on 0800 699888 will do the trick.
Just ask them if they can activate Online Traffic Services and it will be switched on in @24 hours.
You will then see the Online symbol on the lower left of the MMI screen and Audi CS will confirm via email also.
I done this on my 2011 @6 months ago and on my 2014 earlier this week.
Free 12 months Traffic Service seems a good thing for me despite me preferring to use Google Earth!
-=Glyn=-