No, but you might negatively impact the user experience of someone else in your cell sector. It's about system design. Your phone is just a way to access AT&T's wireless network. As the designer of that system, AT&T is entitled to control how your devices access it to optimize overall performance.
Then the designer did a shitty job. They should be throttling at the towers if and when doing so is necessary. They shouldn't have devices (which by definition they cannot trust to do the right thing) do the throttling for them -- especially when they don't even have all devices (e.g. Android) set up to do throttling.
