Try not to yell, this is where you either type in all capitals or use text editing to increase the font size and bold type of your message.
If that doesn't work usually it's best to address someone with a question.
For example, to ask someone a question you may want to use this format to do it and to talk to others the same way: Person's name: Your question Most of the time you will get someone's attention this way.
All I can say is, cheating through a computer is ridiculous, but unfortunately it happens.
And like I mentioned of other stuff happening, they can also be messing around with someone not on-line and totally stabbing you in the back.
Just keep in mind however that things can happen in a chat just as they do outside. Just as the name implies, cheating can happen on a computer just as in real life.