ALARM SYSTEM HACKED

Hi there, 

I have had all types of problems with our home security system within the past three months.  We've even had our entire system revamped by adding all new equipment and setting up different passwords as well.  Well today, I received a text message on my iPhone stating "How do you like me setting off your alarm system? (several cuss words were added that I dare not repeat on this thread).  I have notified my carrier, a representative at Apple and no one seems to know how these people keep sending me text messages and now they're remotely setting off my alarm system and bragging about it on top of that.  We have solid proof to what had happened.  I have been with you all since 2006 and we have never experienced anything like this before.  We are concerned about these same people being able to turn our alarm on and off or either accessing our cameras remotely as well.  Now, we're are at a point where we do not feel safe with all of this happening. 
At this time, we are very concerned about what may happened during the holidays if this issue isn't resolved soon.  Need a response to this matter.