Does speaking with one of one's parents during a supererogatory prayer invalidate it, such as when the father asks for a key and you answer?

The question consists of two issues: the ruling on answering a parent if he calls his son while the latter is performing a supererogatory prayer, and whether the supererogatory prayer is invalidated by this speech? The intent behind the permissibility of speech here is to interrupt the prayer and answer the parents, not to answer and then continue the prayer. For intentionally speaking during prayer invalidates it, whether it is a supererogatory or an obligatory prayer.