Occasionally it's fun to take work calls while getting a blowjob from a hot young thing.
But yeah, it's ridiculously rude for a provider to do anything with her phone except silence it should she have accidentally forgotten to prior. I've been with some girls who just don't seem to get it though.
One had her phone beeping and buzzing on the nightstand the whole session and then immediately after we're finished, instead of conversation, snuggletime, massage, round two, etc. she immediately gets on her phone and stays on it for almost all of the remaining minutes.
Not cool...