The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

These two, they have no COURTESY.
Game of Thrones Season 2, Episode 2

I'd thank you to extend me
the same COURTESY.
The Big Bang Theory Season 4, Episode 22

- I've only shown it to you as a COURTESY.
- A COURTESY?!
Game of Thrones Season 1, Episode 8

This is not a COURTESY call, Professor.
Money Heist Season 1, Episode 4

- Father, please...
- I need lessons in COURTESY from you, bastard?
Game of Thrones Season 1, Episode 9