Now, it's not completely illogical. Its very very rare but not totally unrealistic.
Many upscale hotels, if I am correct have telephones installed in the bathrooms. I think its because of safety and convenience. Its actually mandatory in some hotels.
One of my uncles had a telephone installed in the bathroom in his house until a few years ago. I don't know the reason exactly but think it's because of safety. What if someone trips and injures themselves or has a stroke?
Its not completely unreasonable, but it was still hilarious.😆 Granted the Malhotras have money, but still telephone in the bathroom? Must say, they are really resourceful😆