I think that there are several different issues here.
The first one is having unfiltered internet, with full access to all the shmutz in the world. This is simply and unequivocally assur. The Gedolim and venerated Poskim of our generation (R’ Shteinman, R’ Vozner, R’ Chaim, R’ Nissin Karelitz, R’ Moshe Shternbuch, to name a few) have said so time and time again, and I have yet to hear a single dissenting opinion. (see: http://www.theyeshivaworld.com/news/headlines-breaking-stories/285798/maran-harav-shteinman-iphone-users-are-pasul-leidus.html, http://www.theyeshivaworld.com/news/headlines-breaking-stories/207517/r-kanievsky-on-accepting-eidus-from-an-iphone-user.html)
Secondly, when it comes to something that is assur, saying “I need it for my business” simply will not change anything. Business is not an excuse for any issurim; be they chillul shabbos, dishonesty, or unfiltered internet. Assur is assur. Period.
Then there is a separate issue: Having a smartphone, with properly filtered internet, for business needs. While this may not be ideal, it is indeed often necessary in today’s world. And when it comes to ideals, not issurim, there is much more room to accommodate practical necessities.