Cancellation Process

I spoke to a Cool ideas consultant on the 1st of April 2021, i asked for my subscription to be cancelled. I proivded them with 1 months notice and the requested. however now when i called them they say they did not recieve the mail so i must pay my monthly premuim again. Poor cancelation process from Cool ideas and seemts like such a mission. I want my fibre line cancelled immedialty or by the 1st May as reqeusted. i have proof of my mail sent as well.