Not that I'd be interested in that shit even if I was a Japanese person living in Japan, but I find it really creepy a host/hostess club employee would keep calling or messaging clients, to keep bringing them back. Of course it is that kind of business, where at worst the whole purpose is to exploit the weaknesses in the client's character, to suck them dry of money. So, saying it's not professional behavior would be incorrect, but at the same time, if you compare it to the whole world of service businesses, it would obviously be extremely unpleasant. Unless you are mentally sick, like that Kanon girl here.