Refusal to abide by Consumer Protection Act

Bought Siemens tumble dryer in June 2015 - it stopped working on 18 October. I reported it to Ivan's in Claremont where I bought it and he logged a guarantor service. Technician found the door lock/door knob faulty. Given fact machine only bought recently and fact that have barely used it, have a Siemens dishwasher and washing machine that have given no hassles, have no confidence in machine and fear it may be a dud I requested that it be exchanged for a new tumble dryer as is my right under the Consumer Protection Act which trumps all \store policies"\""brand warranties\"" etc. Siemens are refusing to do so"