Change tags with col.gameObject.tag inside an OnTriggerEnter function NOT WORKING

Questions & Answers
1

My objective is this: When objectA enters the objectBs collider (objectA CAN penetrate objectB), the tag of objectA changes or not, depending on objectAs current tag. This is accomplished by a script attached to objectB (the comments are what I EXPECTED the script to do):

var tagChangeNA: GameObject; // sound played when the tag change is NOT possible
var tagChanged: GameObject; // sound played when the tag change IS possible

function OnTriggerEnter (col: Collider) { //the following will be done when objectA enters object Bs collider

    if (col.gameObject.tag == "Cold"){ //if objectAs tag is Cold...
    Instantiate(tagChanged); // play this sound
    col.gameObject.tag = "Medium"; //change the objectAs tag to Medium
    Destroy(gameObject); //destroy objectB
    }

    if (col.gameObject.tag == "Medium"){
    Instantiate(tagChanged); // play this sound
    col.gameObject.tag = "Hot"; //change the objectAs tag to Hot
    Destroy(gameObject); //destroy objectB
    }

    if (col.gameObject.tag !="Cold" || col.gameObject.tag !="Medium"){ //if the objectAs tag is something else...
    Instantiate(tagChangeNA); // actually dont do anything. Only play this sound.
}
}

THIS SCRIPT DOES NOT WORK AS EXPECTED. What happens is:

I control objectA to enter objectBs collider.

The initial tag of objectA is "Cold".

When I enter objectB, objectB gets destroyed NO MATTER WHAT objectA's TAG IS (EVEN COMPLETELY IRRELEVANT TAGS)

Both sounds are instantiated (tagChanged & tagChangedNA) simultaneously.

objectAs tag DOES NOT CHANGE.

I really cannot understand why it works in this crazy way.

What am I missing here?

NOTE: both objects are Prefabs, they have Rigid Body component attached and the tags mentioned are already defined in the tags list.

2

The script is OK, there was another script running on objectA that prevented tags changes. Sorry to anyone who spent their time trying to figure it out!