Poor service supersonic

SUPERSONIC,!!!! Not supersonic, its supposed to be super pathetic! Please can anyone help me i send through my cancellation request a week ago and still nobody have phoned me. Please how do i get rid of supersonic as my ISP as i want to use someone els but cant as supersonic needs to release my fibre line. I want out as quickly as possible... they do not get back and even when they do they are just apologetic with no reel solution or fix. I have send through the cancelation request twice but still no call????? We have no fibre between 19:00 till after midnight every night for the past 3 weeks. After numerous calls and messages and 2 cancellation request later i just want out!