Just a bit of advice from someone who purchased a Telcell SIM card.
I had nothing but trouble the last 4 days with our trip because of Telcell. They're service for some reason could not connect with any (847) area code and most of our numbers started with that code. We went to their office twice for some help and were given none. The people in the TC office were having the same problem with their own phones. I don't know if this is fixed but there wasn't any problems with the Chippie card.