Pathetic Customer service

I signed up with Sadv for a Fibre connection and because of the issues with my aunt's bank details I gave them mine and the guy promised to send me a link so that we could update the bank details later in the month. Later in the month there was still no link sent, I tried contacting him and he still promised to send the link and nothing was sent. I then kept in contact with the guy asking him to sort this out, he promised to get back to me but never did. After a week or so, he asked that I reverse the payment but the bank did not give me an option to do that. He then advised that I should withdraw all the money in my account so that it bounces back which I refused to do because the bank charges for all the debit orders that bounce back. I kept asking that he sorts this out but he then decided to stop responding to my texts. I then logged into SAdv website to register and then tried changing the banking details. I called the company the next day wanting to check if the update was done, I was advised to wait for 5 days and after 5 days check if the banking details had been updated. I did that and the details had been updated but to my surprise, the money was still debited from the old account even after updating the profile with the new banking details. I am now not sure what to do as the calls are never answered and the tickets logged are never attended to.