Alison DiLaurentis has had five phones throughout the show. She uses her phone, to keep in touch with her friends and family, use the internet and receive A's Messages. Currently, she has an iPhone 6 Plus.

Motorola V3i

In the Season 2 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 3GS

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

Burner Phone

Later in "EscApe From New York", she uses a burner phone in New York which she bought from a convenience store

iPhone 4S

In "Thrown From The Ride", you see Alison texting Emily with a white iPhone 4S in a white case. She uses that from season 5 to season 6A.

iPhone 6 Plus

In "We've All Got Baggage", you can see Alison reading her text from Uber A on a white/silver iPhone 6 Plus in a pink damask case.