Battle to cancel policy with Dialdirect

I have been a client of Dialdirect’s for a number of years. Every year I have to argue with them about what my premium amount should be since they increase it exorbitantly every year. I’ve just been trying to cancel my insurance with them since I’m changing to another company (and was required to send them a cancellation letter) but they will not respond via email, so I phoned them. The consultant kept me on the phone, asking me over and over again why I was cancelling and telling me why I should stay. He did not acknowledge or apologise for any of the reasons I had given to him as to why I was cancelling my policy. In a nutshell, he didn’t allow me to cancel my policy and now I have to battle to try and find another way to cancel it since they are not meeting my request via email or telephonically.