Yes, there is.
Ban a user

Or at least I thought there was. I've never actually bothered to block someone but I've seen people say they've done it.

How? Is the system not taking random users?
It's not random, people see your challenge and accept it.
It's not random, people see your challenge and accept it.
When you click on Start game, i assume is sending a challange and the first user with the same settings will join the game. (In this instance i'm wondering if i can block a user from join the game)

Not true, there is a board with all challenges that a user can choose from and he clicks on one someone else started.
Not sure how to block someone.
I know about the board, you can choose a challange there, but if u click on start game i think it picks random

Go to account/privacy and block a usernme.....
Once blocked, a member cannot do any of the following:
- post notes to your account
- send you messages
- accept your game seeks
- be auto-matched with you in open seeks
- join tournaments that you are running
- post in content that you created

It's too much of a hassle.
It would be nice to have access to fine-grained ban control/filtering from from the live chess interface.
Think about how optimal you could make your experience and configure your trade offs with such a thing. It would be revolutionary. Then patent it, and chess.com will be untouchable.
Paul

I think if you block user then he will not see your challenges anymore.
As there are a lot of nonsense people I have blocked a lot of users and dont't have run across them anymore since then.

The OP (Oniyris- or some such silly name) deserves to be banned for sure. He disconnected in an unrated game to avoid an unavoidable checkmate. What a jerk to inquire about banning someone. An did I say he's a weak player?
Is there an option to ban a specific user when paying live chess?