Alison's Phone

Alison DiLaurentis had three phones through this show. She used her phone, to keep in touch with Ezra Fitz, Ian Thomas, and her friends and family, use the internet and receive A's Messages. Currently, she has a Burner Phone.

Motorola V3i
In the second season Halloween episode, "The First Secret," or earlier, after Alison meets Jenna in Halloween costume shop, she receives a message from "A" on her pink, Motorola V3i cell phone.

iPhone 3G
A year later, in Pilot, "A is for Answers," after she threatens to Jenna stop threating her, Alison receives a messages from "A" on her iPhone 3G with a black case.

Burner Phone
Later in EscApe From New York and possibly future episodes she uses a burner phone in New York.

iPhone 4S
In Thrown From The Ride you see Alison texting Emily with a white iPhone 4S that doesn't have a case.