Australian Car Repair Issues? Ask an Auto Mechanic for Answers ASAP
1st try resetting the ECU by disconnecting the battery cables and clamping them together for 10 mins. Remove both battery leads from the battery then use a nut and bolt or G-clamp to hold both battery lead terminals together.
This discharges any capacitors / memory within the ECU and around the car so ensures all memory settings are wiped clear - back to the factory default.
This will reset all the systems on the car and you may need the radio security code to get it going again, and ensure that the keys are in your hand when you re-connect the battery as the car may lock and turn on the alarm
in that case
Find the alarm cancel switch - it's on the facia to the right of the steering wheel, has a picture of crossed out speaker on it. Lock the car, then unlock it again, open the door, put the key in and turn on the ignition, then press the alarm cancel button - you need to do this within 10s of opening the door (not exactly sure on this - you might need to press the button on hold it in whilst turning the ignition on.)
this should reset the alarm
do you have a key switch anywhere on the fascia or on the end of the dashboard? , where you open the doors and then view the end of the dash, some model have the switch here