Makro ****med me

I bought a zero appliances 6 burner gas stove from makro For R6349. 00 and unfortunately it is not not working properly, when I bake with the oven of the stove, the scones don't get done on top but they burn underneath, I request for a returned, they declined,I then logged in another return, they declined and told me that my warranty has become null and void because I used the stove for commercial use, but the sscmo disclaimer that states that the stove is not for commercial /Domestic use.. Please help me get my R6350 back.