Success.
So, the people at the store were...useless. "We've had tons of Cingular customers, and they've never been charged." Well, that's peachy, they're charging me. "Well, you can either call them and beg them to waive it, or just switch back and they'll waive it."

The whole point was to get away from them, plus YOU gave me wrong info, YOU fix it. Nope.
So I called Sprint CS directly. The CSR says, "Oh, you'll have to talk to the store, we can't do anything." Uhhh, lemme talk to a supervisor. "They can't do anything for you. Still want to talk to one?"

YES.
In the process of transfering to a supervisor...I get cut off. Joy.
But, that actually worked out for the best. I called back immediately, got a different CSR. I told her I just got cut off while being transferred to a supervisor, she asked what the problem was. Her response was, "Oh, wow, that's not good. I've got a supervisor standing next to me, one sec." She put me on mute, and a minute later came back and said the $350 would be credited to my account. And then asked for the store's phone number and the sales person's name.
It took a little, but I finally talked to the right person. Thanks Jill!