Hitachi Ac - asking for payment for under warranty

I purchased window Hitachi window AC which was installed by Hitachi.
Later I felt that the AC is not cooling well and I made a complaint. Technician came and checked. He stated that that cooling is well but when I said him to check the room temperature he which was not cool. He did not say about that. Also he noted the current of AC which was *.* against rated *.* A. he said he will check further. But he closed the complaint.
Later again I observed LC indication on panel. My child was playing with the remote a bit before. I though by mistake it was locked. I further lodged complaint (***********) about this. The technician came and tried to reset the unit for ** minutes but he failed. He further said the program is locked and it is beyond capacity of a child to lock this. The unit was deliberately locked by me. He will charge Rs *** to unlock it. It is noteworthy that on first day I tried to set password for unit as per user manual but I failed.
I made my further submission to customer care and requested that any technical person should answer
*. Why Hitachi has made program code access so simple that any one whether an adult or child can access it (program access code is not accessible to general public). Has Hitachi any agenda to trap customers to lock the unit by mistake and make money by charging?
*. Even if the unit is locked by mistake, why Hitachi not provided any interface for adult customer to reset by own. The only mean left is to call technician and that is chargeable.