Unable to block ****** device

A phone which I bought for a friend was ****** so I tried to block it as advised by their help page by dialling 082135. Nowhere in the audio prompts is their an option to block a phone nor is there any option to speak to an agent. It seems like they are doing all they can so you cannot speak to anyone. I then sent an email on the 20th Feb listing my issues and asked to be called back. All I got from them was what looks like an automated response. Since then have sent 2 more emails and I only get the automated response back. How can I block my ****** device?