technician apointment failed!!

I ordered my dsl online since Feb 13 it takes 2 months before my router arrived in my post..and April 19 o2 send me on my email that they scheduled April 28 for technicians ro come and install they give me time from 12:00 till 16:00 I waited till 18:00 but nobody came..can somebody help me what should I do? I chat online for o2 to ask help they keep on telling me that an employee English speaking will call me back I waited till 20:00 but they didn't call so I chat again they told me they will call me back tomorrow and this makes my blood boil! !