Hisense Smart TV 50 Inch

My tv is automatically switching off and on , I logged an issue with Hisense , they sent me technician , for the first visit he updated TV software , second visit he changed the motherboard , couple of hours after he changed motherboard I experience the same issue . Now I just received an sms saying my job is complete , the issue is not fixed

I called the call center , they telling me they will send the third technician , I dont want the third technician I want my money back . I can not keep a TV that is less then 2 years and you guys tried to fix it twice already.... that a risk . PLEASE COME TAKE YOU TV I DONT WANT IT ANYMORE AND REFUND ME