Paying for nothing

2.5 weeks after signing still endless connectivity problems. No assistance available over weekends though it is advertised. 5 days ago they logged a fault with Openserv Fibre to get back to me within 24-48 hours. Instead of resolving any problem the Fibre box went 'dead for 3 days now. Yet when I want to cancel as am already billed for use of service I am told I must give one calendar month notice thus must remain without any service/product and pay for NOTHING IN ADVANCE.