Free sex in LOL

Look, I don’t know why I found this joke so funny, but I’m still laughing at it two days later.
I saw it as a status from some random guy in my newsfeed.
This is how it went…

I asked a Chinese girl for her phone number last night. She goes to me, “Sex! Sex! Sex! Free sex for tonight!”
Her friend had to clarify for me, “She means 666-36429.”