"Why did he not speak to her on the phone?"
Translation:Pourquoi ne lui a-t-il pas parlé au téléphone ?
il a parle is usually translated by the past simple: did he talk/ he talked. il parlait is the imperfect and usually used when an action is repeated in the past or was going on for a while. A common translation using a sentence similar to above might be 'why wasn't he talking to her on the phone?'