alarm goes off when not set?

Hi, i have a optima xm alarm, it was already in the house when i bought it. The alarm will go off if it isnt even set, leaving me having to warn the nieghbours if i go away. Also when i try and set the alarm, the exit audio sound keeps go going, it does not turn on. I have tried exiting and omitting the downstairs zone and this works, but then i only have the alarm on upstairs, is there any one out there who can service and check the system,
Thanks P Harris