ADT SECURITY IS TERRIBLE!!!

In August 2014 I met with an SSG Security rep who came along with an SSG contract, I signed this contract and was fooled into believing this was a monthly contract and could be cancelled whenever necessary due to me renting the property and not owning it. Months went by and I heard nothing from SSG, in December 2014 we had to cancel our lease agreement due to financial strain and I chose to move in with my mother to save with costs to help me support my new arrival. In January 2015 I received a call from my previous Estate Agent needing assistance with the alarm. To my surprise SSG Security had in fact sold all of their contracts over to ADT Security, I called ADT Security and they then informed me of my outstanding balance of over R2000 odd rand, I was shocked and told them my story as above and they have now said I must pay a cancellation fee of over R4000 odd rand for the remainder of the contract that is apparently valid for a 2 year period. I am devastated about this and just cannot afford to pay this due to my financial struggle. Can ADT do this to me on the fact that I heard nothing from them, no service whatsoever until I called them needing assistance with the alarm. :(