Poor after sales service

Bought a brand new microwave oven from Kaysies in Eastlynne. After 10 days it wouldn't switch on and we took it back. I was without it for 3 days and got it back with the exact same problem. Defy then sent a technician to my place who did not find any fault. I phoned Defy yesterday and spoke to Mershia and Ismail who was supposed to come back to me which never happened. I think it is unacceptable to purchase a brand new item and have to send it back 3 times.