Why did my boyfriends baby mama tell him yes then no?

So randomly my boyfriends baby mama contacts him and asks him if he would be interested in taking their child to get dedicated at his church. He agreed then called her and said that it was gonna be on a certain day. She then said no because the day was after he was supposed to bring his son back from visitation. It was basically 2 hours later. He told her it was the only time he could get to do it and then she said that was his problem. Why would she call him, ask him to set something up, then tell him no?

Why did my boyfriends baby mama tell him yes then no?
Post Opinion