If you tell someone off, you speak to them angrily or seriously because they have done something wrong. He never listened to us when we told him off I'm always being told off for being so awkward Dutch police told off two of the gang, aged 10 and 11
If you give someone a telling-off, you tell them that you are very angry with them about something they have done. I got a severe telling off for not phoning him. tellings-off the act of telling someone that they have done something wrong