What happens if I reply to the spam message that begins with unsubscribe 106? It is urgent.

You can reply, but most of them reply "t" and some reply "106", but this 106 may also mean "agree" and "order". What's more, you can't unsubscribe after replying, and those spam messages will still be received. I suggest you add this short message number to the blacklist directly, and just turn on automatic interception at home, so it will be quiet.