Is it permissible for a young man to talk to a young woman with her family's knowledge before the engagement?

A young man's phone call to a non-mahram woman is forbidden without a valid need, as it is a gateway to temptation, even if her family is aware. However, if there is a valid need for the call, it is permissible, provided that temptation is avoided and the conversation is limited to the extent of the need.