I would be surprised if a MK7 needs it yet.
On what basis did they suggest a "service"? What I mean is, what was the criteria that led them to that conclusion? I doubt it was stipulated by VW after xxxx miles/years so I guess the service desk just like to make quick easy money. Unless they confirmed a leak (which should be covered by warranty anyway) I can't see a reason for a service, but I could be wrong
I would list these as the basics
1: Do you use the AC frequently?
2: Does it get to the required temp quickly,
3: Does it blow cold when required?
If the answer is yes, I would save the money.