Apologize and explain

Mum- William! What do you doing?

William- What's the matter? What have I done?

Mum- You have been at the computer during all night!

William- Really? I didn't mean to. I didn't realize that it was morning

Mum- William, you know I don't like it when you spend so much time on the internet.

William- Well, only has happened once.

Mum- WILLIAM!!

William- Ok, ok. Listen, I'm really sorry. Don't worry. It won't happen again, I promise.

Mum- I hope you're right. We'll see.