Go to Logitech's website and look up the support information.
Call Logitech and talk to the nice person on the phone. It's that simple really.
My G110's headphone jack started crackling after 11 months, so they sent me a new G110 with next day shipping via UPS, a discount code to use on future orders, 50%, and said we could dispose of the old keyboard "if we wished".
Best customer support on the planet, they will solve your problem in one phonecall with no hassle.