All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If you are referring to the mourning period of a woman when her husband dies, then it is permissible for the wife whose husband died to answer the phone. However, if the person who is talking to her on the phone is a marriageable man, then she should speak to him only according to the need and she should not speak to him in a soft tone, just like all other women are supposed to talk.
Finally, it should be noted that a woman is not permitted to mourn a person more than three days unless he is her husband in which case she should mourn him for four months and ten days; For more benefit, please refer to Fataawa 88684 and 82015.