Pathetic service

I cancelled my contract on the 20th of June 2021. After numerous e-mail and phone calls my contract was never cancelled. My account is just getting more and they want to blacklist me because I do not pay my account. Its not my fault that they did not do their job. Each time I contact them, I got cut off a few times, all they say is they will phone me back, instead their finance dept is harassing me about my account. Nobody is doing something about the cancellation. I am so fed up with this problem. It is now 6 months. I don't know what to do to get this problem fix. They are pathetic. I will not recommend my family and friends to take out a contract with them.