Translation:Why did he not speak to her on the phone?
If you put "lei" instead of "le" : "Perché non lei ha parlato al telefono?" = Why didn't she speak on the phone?"
Also, most importantly, "le" is a personal pronoun meaning "a lei (to her)" :
- Le voglio dare un regalo. = I want to give her a present.
masculine form is "gli = a lui = to him" :
- Gli ha detto quello. = He/She told him that.
This is the indirect object pronoun 'le' which means 'a lei' or 'to/for her' (depending on context). Here it means 'to her'. If you wanted to say 'to them' it would be 'loro' instead of 'le'.
See http://italian.about.com/library/fare/blfare117a.htm for details.
'le' meaning 'them' (feminine plural) is the direct object pronoun, and is used with transitive verbs. Such as "I invite them" where 'them' is the direct object. Whereas "I talk to her" the her (or in Italian the to her) is the indirect object pronoun.
Specifics on the direct object pronouns are available at http://italian.about.com/library/fare/blfare116a.htm
I agree completely. We speak both 'with' and 'to' people on the phone. They're synonymous. As for UK usage (AncientBat) vs American, I think there's a difference between 'phoning' someone and actually 'talking with/to that person". I mean you could very well phone someone and not actually get to talk with that person because e.g., the person is out or doesn't answer the phone. "He phoned her, but she didn't answer."