Failure to respond in time - resulting in death

We installed an alarm system recently, and were told that they offer a medical emergency service where we can get an ambulance within 10-15 minutes. That was the reason we took the system. My gran fell ill last Monday, 11 May and we pressed the button for medical. No one responded, no ambulance arrived. After a friend called and screamed at them, they called me. An ambulance arrived here after 9pm, we first pressed the button at 7:30pm. My gran had a stroke in our home and stopped breathing, with no pulse. We got her to start breathing again. When we eventually got her to hospital, she suffered a 2nd stroke and passed away. This episode has left my entire family severely traumatised and adt failed to call us after this incident even though I asked the guard to relay the message to them. They did not call at all. I had to call them on the Thursday after that, & they didn't return my call until I called again. I was then informed that their finance dept will contact me, nothing has happened yet. I called today, 19 May & I was on hold with no answer. I need them to resolve this, they cost me the life of my gran! They need to come to my house and speak to me or I will take this further