No; in fact, when AT&T switched from unlimited to metered bandwidth pricing for iPhone plans, 95% of customers (including me) saw that they had to pay less per month. The private market is simply not so broken for cellular telecoms right now that AT&T can charge a lot more than their costs for things like bandwidth: they are actually in fierce competition with Verizon, and for the vast vast majority of users the only thing they care about when choosing between these two companies is price.

Five years ago this was not as true as it is today, as at the high-end of the market (so only people with a lot of money to burn) people would sometimes select carriers based on what phones were available (hence the value of the AT&T-exclusive iPhone), but with a world where handset manufacturers carry most of the power (and in fact get even a good percentage of the money paid to carriers, due to the subsidy) and all of the best phones are available for every major carrier, this no longer matters: carriers are now dumb pipes to everyone but a small percentage of people living in an area with a major coverage disparity.