Audi a3 air con help re gassed but hissing

Just had my a3 quattro regassed however they said i had a leak and wouldnt charge me , on lifting the bonnett straight after there was a loud hissing noise which seemed to be top of engine at the front it was quiet loud untill it eventually stopped.
Any idea what this could be is it liable to be expensive job ? the air con did work for about 1hr untill i guess it was empty of gass.
thanks
colin

Yes Colin, there is obviously a nasty leak in the aircon system. This could be as simple as tightening a joint in the plumbing, or as serious as the aircon pump seals being knackered. Take it to a specialist asap and have them test and diagnose what is happening. Good luck on this one.

Yeap I'd agree, get a pro to look at it.