Continuity mistake: When Toby comes to get the chipmunks at school he breaks a drum-head. He breaks the same drum-head twice.
Alvin and the Chipmunks: The Squeakquel (2009)
Ending / spoiler
Starring: Justin Long, Jason Lee, Zachary Levi, David Cross
Alvin and the Chippettes reunite with Simon and Theodore, and Sabe, too, in the concert in a toy helicopter. Returning home, Alvin and the chipmunks go to sleep.
Answer: Alvin could have easily known Toby's number and told it to her. Ian just simply put down his phone not even thinking that the chipettes could get at it from inside of the carrier.