I have drive my Cerato 1.6 for almost 2 month . Almost perfect except i just found there is a new defect/problem.

I use my key to lock my car. I found the car was lock but my car was wide open .
I was expecting my car horn/alarm to make noise but nothing happen .
Is this a defect ?

I even try to ask my friend to sit inside the car while i lock the car using the key . it lock . She then open the car from inside and the car open ... No alarm ?

This car does not make any noise . Pls help to advice