DEFY's customer service sucks!

I am experiencing major problems with Defy. We bought a Grundig gas stove and under counter electric over from Tafelberg Furnishers (Parklands branch) approximately two years ago. The appliance came with a 5 year warranty. About a month ago, the oven started playing up - it did not heat properly/evenly. A service call was made to Tafelberg Furnishers and I was given a reference number. About two weeks after that, two technicians called, and arrived on site to "test" the oven. They asked whether we had a thermometer, because theirs was taken by someone else and they did not have one. After "determining" that it was a faulty thermostat, they left, promising to return one week later. It s now THREE WEEKS later! Numerous follow-up calls to Tafelberg Furnishers, and no satisfactory response yet. Jamie-Lee from Tafelberg tells me that Defy does not respond to their calls nor to their emails. I told them that, if it is not fixed by tomorrow, I want either a refund or a new oven I think Tafelberg has tried all they can, and I appreciate their efforts (even though it still did not solve the problem), but... DEFY, your non-existent customer service sucks!!