Mark on oven glass

Good day.On 2015/09/04 i bought a Defy Gemeni Gourmet multifunction from Game at Carnaval mall in Brakpan.The oven was covered with plastic and side protection .On arrival at home and open the plastic i saw that there is a mark on the top oven glass.It is not broken or scratch ,it looks like a durty mark.I try to clean it but it looks like it is in the glass.What i want to know is how do a product go throw your Quality control Dep without picking up this.If a client pays R9499.99 for something they expect better than this.I will not take back the oven because of inconvenient issues.but i think this is very bad and that you must step up your game.