what happens when I just dial the "star" key on my phone?

[AC Question]

I recently accidentally dialed the "star" key on my lg optimus l9 and and I got a message saying something like running ussd, I quickly tried to exit the call or whatever it was but I just wanted to know, did I mess something up on my phone? What exactly happens when you dial "star"?

 

[belodion]

I just dialled it, and nothing happened. Did you dial other things as well?

 

[chanchan05]

Nothing should happen. USSD is just a network service. If no USSD codes match, there's no difference to it and dialing a nonexistent number.