Webafrica goes back on their word, very poor service

Extremely poor service from Webafrica. I was told on 3 October, when I cancelled my fibre service, that the cancellation period was 30 to 31 days, and that I would pay for November but would then be credited for the difference from 3 November to 30 November. I have this in writing. After paying the full amount on 1 November, I contacted Webafrica to confirm that I would receive a credit. I was then informed by a consultant that I would not be credited, and would pay for the whole of November regardless. She would not connect me with a supervisor and simply said there is nothing she can do. Completely unacceptable.