City of Heavenly Fire by Cassandra Clare
Jace shrugged. "Guys don’t let other guys keep calling other guys. Okay, that came out wrong. Friends don't let friends keep calling their exes and hanging up. Seriously. You have to stop."
Alec looked furious. "So you broke my brand new phone? Thanks a lot."
Jace smiled serenely and lay back on the grass. "You're welcome."
"I think," Jace said, "that you don’t want to tell your secrets, so you decided to break up with Alec because..."