No Customer Service!

I terminated my contract with ADT on March 15. I still have not had a response from ADT either via email or phone. I phoned the customer service centre multiple times, the only response is that someone will phone me back. Nothing happened up until today. The contract stipulates a 20 working day notice period - half of that notice period has already lapsed and ADT hasn't even taken note of my termination! I am glad I moved to another service provider!