Refusing To Cancel Subscription And Refund

I'm so disappointed with the service I got from Opix also known as iHappifyfibre via my company. I had an account with them and then cancelled the subscription in September 2022 due to bad internet connection. I received confirmation of my cancellation being received from them dated back in September 2022, however they have continued debiting our account till date. I have called and requested a refund and the accounts manager is continually unable to take my calls and not responding to my emails. They have been happy debiting from our account since cancellation and refuse to refund us what is rightfully ours.