the aircon unit memang no gas when u first buy, as part of installation the standard fee should already include filling up the gas and the copper connection up to a certain length first time

there are many dishonest installers who try to get more from u by claiming they need to fill 'special' gas or in your case langsung no gas. some will claim copper not long enough and charge u a massive free for extension.

next time if u r in a position to find other installers, just ask them to fark off. if u don't want the trouble or might be in danger fighting with them then just pay the fee