14 Days with no with Internet due to ISP holding the Line

My Dad gave notification on the 31st July 2021 o cancel the service at the end of 31 August 2021. They disconnected us and the line is still active with Vumatel. Each time we called we get disconnected and the reference number they gave us was for a different customer with a different address. They insisting that is the correct ref number and then they say will look into it and nobody gets back to us. It's 14 days later and we still got no internet. It's so sad to see what an ISP can do to their customers when once they leave. I always say treat your customers right and they will come back in future but the service we getting here we sadly regret being with Vox. Can someone please help us to get this resolved as it looks bad for your business.