CDA Appliances

I bought CDA through Wren Kitchen, since installed Aug 2018 it has never worked correctly, CDA engineer came to repair it 5 times, now they informed me they will not repair or replace the oven due to the engineers last report no ventilation, that is not the case, they agreed to refund me last week and was to ring me today, no one rang, I rang them for an update to be informed they are not replacing, refunding me, I’m absolutely fuming, the oven has never worked properly, now I have no oven to use I have a family and this is disgusting and not professional.