Poor service

The service received is not great, as a new client I thought they will atleast try and impress me...I app**** for their service the installation happen from 19th until 21st February!! Now it's the 25 February have been waiting for a delivery from their courier for 2days it keeps saying out for delivery. I have no connection and I need fibre to work from home..How and where do I cancel this contract? The service is not what I expected