Bad services

On the 26th Jan i came home only to find that my alarm has been activated but i did not get a call from Adt to check if everything was alright from my side, so I called adt the same and only to find our that they are not picking up the alarm signal on their side, the person i spoke to said they will have to send a technician out to come and check sunday i waited and monday did not go to work i phoned again and they promised the matter has been escalated and a technician will come through, Tuesday i home again and no one came, Wednesday i was back at work and someone from Adt phoned to ask if im home cause the technician is on its way!!!! What! I said im at work and i work far and would not be home for the rest of the week, and i ask if the technician can come on Saturday, i was told technicians only work Monday to Friday until 5pm if i want them to come after hours they can send a standby technician at a fee of R850! Till today no one from from Adt has contacted me or been to my house to fix the alarm.... i want to cancel this damn contract and i dont know how, im paying for an alarm that is not working, please help!