Nightmare experience

Worst service I have received in ages. App**** for fibre connection months ago. No one has pitched up to install fibre. But they were nagging me with promotions and eager to send me a router. Now I want to cancel but there are no options to cancel and they make you speak to a robot who isn't even trying to be helpful. Can't apply with another ISP cause they won't allow anyone else to take over even though they have not interest in fulfilling the order. Where can I report these people for shady business practices.