Garage Cabinets, Garage Storage, and Garage Organization

Hi, I've been driving the car for about 2 weeks now and only just noticed that when i leave the car and think that i have locked it, the rear doors are still unlocked and able to open. On the inside of the door there is what looks like a child lock catch, i tried turning this in the opposite direction to see if that was the cause of the problem, but then it ends up that im able to lock the doors but unable to open them. (have to pull the lever inside and outside at the same time to get the door to open)
If anybody could help me, i'd really appreciate it.