Frown off

Let's decipher.

You were punished with a [duration of time] temporary ban because you failed to choose a champion.

If your connection dropped out (maybe your WiFi is unstable) while you were supposed to be choosing a champion, there is nothing they can do.

The rules for champion selection is that a person who doesn't chose a champion before the time runs out causes the match to be cancelled. The person responsible for causing matches to get cancelled receives a penalty for making other people waste their time while they were forced to sit there as you did nothing. Trolls might do this for fun to make people upset, so just in case, you get a penalty.

If you abandon matches, it's the same thing.