What did I do now?
 

I was told that this is wrong, but the teacher is out so I am posting here.

Dila tu número. = Tell her your number. (Command)

You're using a direct object pronoun. You need an indirect object one instead.

That's funny - I didn't see the Spanish, but looked at the title, which to me is quite incorrect. But I guess it's American usage of the simple past, where English usage would be the perfect tense. (What have I done now?).

Anyway - getting back to the Spanish - is that an example of laísmo ?

It could be, although I have never seen it used with the imperative form. :thinking:
I usually find "laísmo" in sentences like:

- La dije que viniera. -> Le dije que viniera.
- La di un beso. -> Le di un beso.
- La conté que tengo un nuevo empleo. -> Le conté que tengo un nuevo empleo.