Air con oil? Denso oil compulsory?

[Goran]

I need your help please.
I went to ATS Euromaster to get my aircon re-charged using a Groupon, but the service manager told me he couldnt do it because their system says Audi must use Denso oil, and they use PAG oil. He was worried about damaging my car.
Is this true, does it really have to be this Denso oil?

Now I know many of you have had your aircon re charged using independent garages, have all of them had this Denso oil? Or is this PAG oil fine?

If its fine I'll just re-book with Euromaster. I dont really want to pay Dealer prices just to get Denso oil.

Thanks in advance.