Advertise one price and sell in store for more exspensive price

I saw on the internet Game have a special on Ryobi Cordless Drill 12 Volt for R399, I phoned the stores around me they confirm they have stock on exactly the same drill but the price is R499. How can you advertise a product for R399 and then sell it in store for R499. And then you kindly add on the special paper Delivery can be arranged to your preferred store. You DO have stock but you sell them for R100 more, please tell me how this work????