Update for future visitors and googlers.

It was quite easy to get an entel nano sim for my Iphone 6. Cost only a few dollars. I loaded it with 1 gb data for 8000 CLP. The only annoying thing is that is the most you can load at one time. I had to reload it and you can't go to an entel store to re-load. You need to find a grocery store, or small phone dealer that sells reloads.

Other than that it worked all over quite well. Worked very well on Easter Island and had no issues in Punta Arenas/Puerto Natales....and no there's no service in Torres del Paine but why would you want to be on your phone in such a beautiful place (I checked when leaving on the bus).