Shaykh Fath Al-Qadasi was asked:

Question:

Assalamu Alaykum wa rahmatullahi wa barakatuhu. One of the brothers asks: what is the ruling on using the cell phone inside the masjid? That is: calling/making calls. May Allah reward you with good

‎وعليكم السلام ورحمة الله وبركاته

‎إن احتاج إليه ولم يؤذ في المسجد ولم يرفع صوته فمباح

Answer: “Wa Alaykum as-Salam wa rahmatullahi wa barakatuhu. If he needs it, and he does not harm [others] in the masjid, and he does not raise his voice, then it is permissible”

Translated by

Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan