Shaykh Bin Baaz (rahimahullaah) was asked regarding the ruling of speaking in the bathroom while using the toilet.
He (rahimahullaah) replied:
If there is a need for it then it is all right, but if there is no need then it is better to leave it. If it is necessary to call someone, or say “do this and that”, then there is nothing wrong in it.
Source: http://www.binbaz.org.sa/mat/20858
Also Shaykh Muqbil (rahimahullaah) gave a similar fatwa, as found in his book, ‘Qaaratul Ashritah ‘ala Ahlil Jahl wa-Safsatah’.