What is the ruling on speaking on a mobile phone inside the bathroom (restrooms) while relieving oneself or speaking with those outside the bathroom?

One should not speak inside the bathroom, especially if there is no need to, as the speaker might mention Allah Almighty, and it is not prescribed to mention Him in such an unclean place. As for during the act of relieving oneself, speaking is disliked unless there is a benefit, and silence is recommended unless it is for an important matter. So, if one sneezes, one should praise Allah with one's heart only. If one speaks but does not hear oneself, there is no dislike.