Faulty appliance and unsatisfactory service from OK Furnitures

I bought a Defy four plates built in stove at OK last year, the stove stopped working sometime beginning of February 2019 my sister phoned OK and informed them of what the situation is and they said a technician from Defy will be sent within 5 working day; we waited almost 2 weeks. They fixed the stove in February and Beginning of March (08/03/2019) I was informed by my sister that the oven has stopped working I tried to phone OK Furniture store on Monday and both the Manager and his assistant were not available the whole day. This morning the 12/03/2019 I phone again and the assistant manager insist that they will ask Defy to send a technician again and I refuse to have the stove fixed again infact I want them to replace it because I cannot be having such issues with a brand new stove that's less that a year old and the lady was not that much helpful. Please can you help me with this because I paid over R4 000 for this stove and no I'm being treated like nothing. I'm so angry and disappointed, please I need assustance.