Is a woman's talking with a man over the phone out of necessity considered an unlawful seclusion (khalwa)?

It is permissible for a woman to speak on the phone with a non-mahram man when there is a need, provided that her speech does not involve a softening of the voice, and this is not considered impermissible khalwah (seclusion). The Sharia regulations mentioned in the Holy Quran must be observed, such as the Almighty’s saying: "And when you ask [his wives] for something, ask them from behind a partition. That is purer for your hearts and their hearts," and His saying, glory be to Him: "Then do not be soft in speech [to men], lest he in whose heart is disease should covet, but speak with appropriate speech."