[Toph has figured out her phone (after someone realized that maybe the blind girl would need help finding the 'accessibility' settings), but she doesn't want to deal with walking anyone else through using it. So hearing that voice on the phone meant she was going to go out listening for a familiar voice in person.]

[She stopped, getting a sense of her surroundings from the echos to guess that there probably wasn't anything that would stop Aang from seeing her, and yelled.]

Hey, Twinkletoes!