Practically every mobile phone carrier in the U.S. has relied on the iPhone to boost their sales numbers and increase customer satisfaction in recent years (sorry, T-Mobile). It turns out that betting on the iPhone isn’t just great because it gives customers the pretty device they want, but converting users into iPhone owners might mean that they will be more likely to stay with your carrier in the long run even when your service sucks. On the other hand, BlackBerry and Android owners are quicker to jump ship when the service has problems.