I just had my aircon refrigerant refilled 2 days back.
The shop is called Gulf Falcon Trading in Industrial Area.

Coming from Woqod in Ain Khaled, go straight to second R/A where Mitsubishi and Nissan repair shops are. Turn left at the R/A.
Go straight on. The shop is on the left side after Ford and Peugeot repair shops and before Bentley shop.
Charge depends on how much gas they put in to refill.
They charged me QR 100.