Method overriding with different parameters

Lets say I have a parent class:

class Parent{
    public void aMethod() {
        //Some stuff
    }
}

and it's child class:

class Child extends Parent {
    public void aMethod(int number){
        //Some other stuff
    }
}

Now the child has both methods with different parameters. This does method overloading. But I need method overriding, i.e, If someone tries to call aMethod() with the object of child class then the method of child class should be called or say method of parent class should not be accessible. But I can't change the access modifier of the parent class because the parent class has other children as well and they need the method as is.

So any suggestions?