Trying to change value of an object but it does not change

I am trying to change a value in below $object but it does not changes.

[hidden:protected] => Array

(
    [0] => id
    [1] => unique_key
    [2] => created_at
    [3] => updated_at
)
...

[attributes:protected] => Array

    (
        [id] => 149
        [date] => 2018-04-29
        [item_id] => 1205
        [description] => xaxa line 1 description
        [quantity] => 123
        [org_amount] => 369
        [org_balance] => 500
        [unique_key] => 15001101000031
    )

[original:protected] => Array

(
    [id] => 149
    [date] => 2018-04-29
    [item_id] => 1205
    [description] => xaxa line 1 description
    [quantity] => 123
    [org_amount] => 369
    [org_balance] => 500
    [unique_key] => 15001101000031
)

...

After I run $object->org_balance = 369 it stay same. And I can not figure out why.

via Chebli Mohamed