Faulty Appliance and Bad Customer Service

On the 7th of September I ordered a kettle from Tomu, after seeing them on Facebook. It arrived 2 days later and I gave them a positive rating. On the 20th I started having problems with the kettle, it wouldn't automatically switch off, and I wrote on their Facebook page. I was asked to record a video and send to support and I did. I got a disappointing response that I should pay to courier it back, and I must wait for the manufacturer to determine if there's a fault and only then will they refund me. I find it absurd: 1. the purchase was done less than a month ago. 2. It's designed to automatically switch off and it doesn't, clearly that's a malfunction fault. 3. I'm told the manufacturer says they've never experienced that, yet the possibility of the kettle not switching off is mentioned in the troubleshooting page of the manual. 4. Surely as a customer I can't be punished for a manufacturing fault, where I have to pay and wait without a kettle, for the manufacturer to decide my fate. I wrote back to Tomu and they haven't responded. I'm not asking for a refund but a replacement. Their service is generally very disappointing and I wouldn't recommend it to anyone.