"When are you going to call me?"
Translation:Quando mi chiamerai?
The present tense is often used to express what will happen in the future. If another element in the sentence refers to the future, the present tense can be used. (http://italian.about.com/od/verbs/a/italian-verbs-present-tense.htm)
- Torni a casa domani? / "Will you go back home tomorrow?"
I think that an element which refers to the future is not necessary all the time, like in this case, so "When are you going to call me?" can me translated as "Quando mi chiami?"