Originally Posted by
UAPremExecflyer
You can purchase a SIM card at the Post Office (La Post) in the Arrivals Hall.
A simple Google search "SIM card Geneva airport" would have turned up that answer in about 30 seconds.
I'm not sure if it was due to the language barrier or something, but 2 years ago when I last visited Geneva I couldn't get a SIM card at the Post Office. Had to eventually go to the Geneva Train station's Swisscom outlet to get one.