Celeste knew that it wasn't the best choice to end the call on Bane. She just didn't want to talk to him anymore with the things he was saying and the mood he was in.
Not only was he not fully human, but he was also obviously part of something to do with a less than legal organization. The most common was the mafia.. She didn't know that much about them except that they weren't the kind of people she would want to get involved with.
She had put her phone down after she ended the call as Bane had tried to call her back, he obviously wasn't ready to end their conversation yet. She didn't feel that she was under any obligation to talk to him and chose to put her phone on 'do not disturb' so that she didn't have to worry hear the phone buzzing each time he tried to call her back.
