"I need to call my friends."
Translation:Necesito llamar a mis amigos.
Yes, it's incorrect because, although some verbs need an a before a following infinitive, necesitar is not one of them. (Necesito llamar .....)
Since the direct object is people (my friends), the personal a goes right before them. (.....a mis amigos.)
In an earlier test ..I need to.. was translated as ...tengo que... I have to. Why is it wrong now?