Cancelling of bad Service

I have been trying to cancel my service and line with them as from the 05/04/2023. I have done it by mail, I have done it by Whatsapp, But yet Service is still on and I still get a bill. Then I get told but I have to pay for my notice month and send a Whatsapp. Evetime I do that the process starts over. So I get on the app pick to cancels my service and then get told sorry you have to give a months notice and pay again. I have stopped paying know as I am not getting anywhere with this and still no cancelation............All I want is to cancel my service and get my line released.