Appalling customer service

I wish to complain about the appalling customer service that I have received. I purchased a defy slimline oven on 30 October 2020 for my investment property. On 9 November 2020 the glass of the oven spontaneously shattered whilst cooking. I reported the incident to the call center on 10 November 2020 and was informed turn around time would be approximately 3 working days. During the course of last week my tenant constantly had to contact the call center to find out progress as neither I nor her were phoned with progress. Only to be told on friday that the technician had picked up the wrong part and only travels once a week to collect parts so we had to wait yet another week. Tomorrow it has been 2 weeks since reporting the incident and still no rectification. The customer service is absolutely appalling and unacceptable. The technicians should take onus on making the mistake of the wrong part and collect the correct one before the normal trip to collect, afterall, the depot is only a 1 hour drive so it would take a few hours out of the schedule to rectify. The call center always says they are escalating, but the technician never responds back to the customer. The call center will not issue the technicians number so we can contact them directly. There is therefore a great lack of communication or gross negligence on the technicians side, either way this is highly unprofessional and has given a very negative perspective on the defy brand.