If you get hold of an eng manual it will tell you how to reset the alarm to defaults, assuming the installer did not lock the code, which is very rare.
I don't think it really appropriate to give out the info on how to do this online TBH, but I am sure you could easily source an eng manual
You will have to re-program the system once defaulted, so would need a little knowledge of how systems are programmed, most of that infor would be in the eng manual too.