I'm confused about data usage. I bought an iPhone 5s with Koodo's Canada-wide Talk + Text ($50/month). It looks like it includes "unlimited messaging" but I have to turn on Cellular on the iPhone and the data usage goes up when I text. Is this part of the "pay-per-use data saver"? Am I going to be charged for the data I use when texting/using the Messages app on the iPhone?