Bennett Read Airfryer Oven

I bought an Airfryer from Builders Market Klerksdorp. After about 1 year, the inside of the oven became like zink and rusts all over. Also the little pan inside started rusting. I contacted them on Internet. They just said I must take the oven back to the store where it was bought, with the slip. That is my problem now....... The ink on the till slip fainted totally!!!!! The oven works very good , but the inside material is SUB STANDARD Now what should I do now?