ADT are useless

We have been a customer of ADT's since October last year. On the two occasions that there have been possible incidents they haven't responded timeously. We are away in the Drakensberg at the moment and a call came through just after 2 saying our alarm has gone off. We asked them to check the property and they promised to call us back. By 4 we hadn't heard back so gave them a call. It took the operator Sibongele a long time just to put our details into the system. She said she would try get in contact with the security guard and call us back. It's now half an hour later and close to 2 hours since our alarm went off without any response back from ADT. This has been the second bad incident with regards to customer service in the last 6 months. They are unreliable, frustrating to deal with and one of the most useless security companies I have ever dealt with. How do I get out of my contract? As far as I am concerned, it's a waste of money.