Hanna Marin currently owns an iPhone 6 in a white case
In Season 1A, Hanna is seen with a Palm Pre.
In Episode 12, "Salt Meets Wound," Hanna is seen with a Palm Pre in a case. Hanna is seen with that phone throughout Season 2.
From "Eye of the Beholder" until the end of the Season 2B, after Hanna threw her Palm Pre in the sink, Mona let her borrow her old Motorola Bravo.
In the Season 3 and onwards, Hanna is seen with a white iPhone 4S in a pink case.
In To Plea or Not to Plea, When Hanna was about to tell Tanner about A. A, hacked into her phone and deleted all the messages she sent her, so there was no proof of her.
In "Of Late I Think of Rosewood" Hanna is seen with an iPhone 6
iPhone 6 (2)
In "The DArkest Knight" Caleb mentions that he can't track Hanna because he gave her a new phone. Her phone is still an iPhone 6 but now with a new case. This may have been because A.D. could've stolen her phone when he kidnapped her
In Hush Hush Sweet Liars, Hanna has an Apple Watch with a silver stainless steel link bracelet band