Supersonic poor service

I have requested a cancellation on my not yet installed fibre that I app**** for end of March. Needless to say, Supersonic cancellations department can not be reached by phone and does not reply to emails. I have requested a cancellation at the beginning of May and to date they have not cancelled the order and this is holding up other fibre installers. Whenever you do get to their customer service department, they simply tell you that the issue will be escalated but then nothing from there on. I had to threaten them with leaving a reply on social media and going to the press before I even received their automated reply. Supersonic gives you an estimate of 14 working days for installation, that was the whole of April, and keeps you updated but after the 14 days are over, they never ever get back to you again. I had to make multiple calls to them to get feedback and everytime the issue would have been escilated and I was promised someone would contact me back. That never happened. I cancelled the contract at the beginning of May (before any installation was done) and to date they have not yet cancelled a thing. Their poor service is now causing delays with other companies who have committed to install my fibre but they can not go-ahead untill Supersonic has done my cancellation. Had I know that it would be so difficult to deal with them, I would have never chosen to do business with them to begin with.