What is the ruling on leaving the mosque during the Friday sermon to answer a phone call, assuming it is urgent, and does that invalidate the prayer?

One who attends Friday prayer must listen to the preacher and refrain from speaking. It is not permissible to leave the mosque during the sermon except out of necessity. One must turn off their phone upon entering the mosque until the end of the prayer. If one forgets and speaks on it or leaves the mosque to speak on it, they have fallen into the prohibition of speaking while the Imam is delivering the sermon, and have exposed themselves to sin, and nullified the reward of their Friday prayer with this idle talk. Even if their prayer is valid, "whoever engages in idle talk, there is no Jumu'ah for him," meaning, they are deprived of the reward of the Friday prayer.