Disappointing service from Rangemaster?

Although I have telephoned, written and emailed them they have only response once to say "we will get back to you".
My five year warranty has just expired and they have the check to write to me to enquiry if I want to take out another year's warranty.
I first contacted them because although I purchased all the correct cleaning materials and a steamer I felt that the cooker was never clean. The numbers on the knobs also just disappeared over a period of time. Someone did come out and although he couldn't really suggest much with the cleaning he said he would send out new knobs. They never arrived. I contacted Rangemaster again when a crack appeared around the top frame. Because it was working correctly they told me not worry it was only cosmetic. My arguement was that every time I cleaned it it got worse and now I have a white crack on the top of the surface. For such an expensive piece of equipment I am very disappointed with the after care service. I would never purchase from them again.